Evaluating Pedestrians' Safety on Urban Intersections

sustainability

Article Evaluating Pedestrians’ Safety on Urban Intersections: A Visibility Analysis

Keila González-Gómez * and María Castro Departamento de Ingeniería del Transporte, Territorio y Urbanismo, Universidad Politécnica de Madrid, 28040 Madrid, Spain; [email protected] * Correspondence: [email protected]; Tel.: +34-910-674-215

Received: 17 October 2019; Accepted: 21 November 2019; Published: 23 November 2019

Abstract: Overall visibility plays a key role in the safety of pedestrians. Despite its importance, verifying the right provisioning of sufficient available sight distances among pedestrians and vulnerable road users (VRUs) is not a prevalent practice. On top of that, the pursuit for more sustainable modes of transportation has promoted the establishment of different shared mobility services which are prone to increase walking and, thus, the number of pedestrians and other VRUs in urban settings. With the intention of verifying how car-centered designs perform for non-motorized users, a 3D procedure that evaluates the visibility of pedestrians and other users is presented and applied to specific cases in Madrid, Spain. The proposed solution employs virtual trajectories of pedestrians with mobility impairments and without them, cyclists, and personal transportation device riders. Their visibility was assessed around the functional area of urban intersections, including zones where possible jaywalking practices might occur. The evaluation was performed three-dimensionally, making use of LiDAR data, GIS tools, and 3D objects. Results show the impact of street furniture location on visibility, the distinctive influence of vegetation on the lines of sight of each observer, and how design parameters that were intended to improve motorized traffic could affect VRU.

Keywords: vulnerable road users; urban intersections; sight distance; road safety; LiDAR models

1. Introduction Walking, cycling, and riding are fundamental to the expansion of sustainable transportation, either used alone or in combination with other types of motorized transport (public transit, private ownership, carsharing, ridesourcing, etc.) [1]. In that sense, the widely adopted tendency of increasing public transit provision and the proliferation of shared mobility services are likely to augment the need for walking and, thus, the number of pedestrians and other vulnerable road users (VRU) in the urban scene [2]. Different bikesharing, motosharing, and shareable electric scooter services have flooded many cities around the world, attracting new users, whether for fun or convenience, with different levels of riding or biking expertise. This trend has altered regular commuting and recreation routes, as well as created new ones [3]. These new users have to coexist with motorized traffic, and they all possess different decision and reaction times, capabilities, speeds, etc. To create safer environments for these dissimilar users, many road authorities have applied different road safety policies, such as speed reductions, traffic calming interventions, among others [4]. Data from Spain’s General Directorate of Traffic show that from 2008 to 2017 accidents with victims increased 3% in urban roads, while rural areas saw a decrease of 2%. Most accidents with victims occurred in urban settings, specifically in streets, with pedestrians constituting 51% of road deaths [5]. Globally, VRUs constitute more than half of the fatalities that occur in all road traffic accidents [6]. For many decades there have been several efforts, from different approaches and fields of knowledge, that aim at decreasing road traffic deaths [7]. From this wide array of studies, some intend to establish

Sustainability 2019, 11, 6630; doi:10.3390/su11236630 www.mdpi.com/journal/sustainability Sustainability 2019, 11, x FOR PEER REVIEW 2 of 16

accidents [6]. For many decades there have been several efforts, from different approaches and fields Sustainabilityof knowledge,2019, 11that, 6630 aim at decreasing road traffic deaths [7]. From this wide array of studies, 2some of 16 intend to establish the relationship between road alignment and profile elements with the occurrence and severity of road accidents [8,9]. Traditionally, the main factors contributing to traffic accidents theare relationshiptackled according between to road the respective alignment andelements profile of elements the road with system the occurrencethey fall into and (vehicle, severity user, of road or accidentsinfrastructure). [8,9]. Traditionally, Some research the focuses main factors on the contributing psychological to aspects traffic accidents behind th aree behavior tackled according of the main to theroad respective users. 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FigureFigure 1.1. DeﬁnitionDefinition ofof thethe availableavailable sightsight distance.distance.

With all these facts taken into consideration, the main purpose of this study is to introduce a procedure aimed at improving the safety of pedestrians and other VRUs in urban settings. First, a method to perform a three-dimensional evaluation of their overall visibility is presented. The factors Sustainability 2019, 11, 6630 3 of 16 utilized to determine their ASD are selected considering distinct VRUs characteristics, such as eye height, lane positioning, and so forth. Pedestrians, with mobility impairments and without them, cyclists and personal transportation device riders (e-scooter riders) are the main observers and targets. Successively, their reciprocal visibility with motorized traffic is assessed. The objects or elements causing visual obstructions are categorized and, on the basis of their nature, corrective measurements are proposed. Lastly, due to the fact that illegal crossings are one of the factors involved in a high concentration of pedestrian-vehicles accidents [5], steps aimed at analyzing road sections prone to jaywalking are described. Other visibility factors with a high impact on pedestrians’ safety and that are related to the weather (rain, fog, snow, etc.), the time of the day (nighttime and daytime), or light conditions are not considered in the presented procedure. The same goes for other human related factors, such as adequate visual search or pedestrian crossing behaviors. The paper is organized as follows: The next section presents the main findings of the literature review, followed by a description of the procedure. Subsequently, the results of its application to distinct intersections are presented and later discussed, and finally, the main conclusions are outlined.

2. Literature Review Of all accidents occurred in Spain in 2017, 63% took place in urban settings. In the last 10 years, while rural and suburban contexts have seen a decrease of 46% in their mortality rates, their urban counterparts have seen a 20% decrease [5]. Moreover, among all the motor vehicle crashes in the United States in 2015, about 53% occurred in a junction or were intersection related. That same year, the two factors related to the majority of fatalities among pedestrians were failure to yield right of way and improper crossing of the roadway or intersection. When it comes to cyclists, the factor involved in a majority of fatalities was that of pedestrians, but the second one was lack of visibility. That study also evidenced motorbike riders as the group of users showing more collisions with fixed objects [15]. E-scooter riders are relatively new to the road scene; thus, no information of their performance was included in the revised data from Spain’s General Directorate of Traffic. One significant factor of pedestrian-vehicle collisions is poor pedestrian conspicuity. This is, pedestrians are not clearly visible to drivers or are detected after the point of no return. As conspicuity depends on engineering, but also behavioral facts, there have been many efforts intended to make VRUs, and especially pedestrians, more noticeable to motorized users [16,17]. Factors related to the built environment include the increase of traffic signals, raised pedestrians’ crossings, and so forth. On the other hand, those intended specifically for the increase of conspicuity include the use of reflective clothing, crossing flags, and so forth. The use of reflective clothing seems to be an underestimated practice that does decrease conspicuity [18,19]. Speed underestimation is another factor with important effects on road safety. VRUs make street-crossing decisions based on their detection of motorized users and their estimation of the speed of oncoming vehicles. The underestimation of incoming traffic speed fosters unsafe behaviors that could lead to conflicts. These misestimations could be enhanced by educational trainings aimed at improving street crossing interactions. Insufficiency of sight distances could affect the efficient execution of basic road maneuvers. On the other hand, in certain road sections, its excess could encourage faster driving, which might lead to road accidents [20,21]. Road transportation agencies have specified minimum values with which users could perform distinct driving tasks comfortably (stopping, crossing, overtaking, etc.), these values ought to be compared against the available ones and if requirements are not met, corrective measures or interventions might be required [11,13,22]. When it comes to intersections, road design guidelines specify the need for clear distances that allow all users to perceive and react to conflicting traffic. Three- and four-legged intersections require sufficient stopping and decision sight distances in combination with clear sight triangles. Roundabouts demand, at least, three fundamental locations to be checked for SSD, in addition to the required ISD [12,14]. The use of LiDAR-derived data to perform sight distance evaluations of existing roads has been an active research topic within the transportation field. Authors consider the capability of performing Sustainability 2019, 11, 6630 4 of 16 the measurements from the safety of an office, as opposed to troublesome field evaluations, a very valuable benefit [23–25]. Some of these previous researches performed the visibility calculations directly on the denoised LiDAR point cloud [13,14] and others employed LiDAR-derived digital models [15,16]. Those that carry out the calculations directly on a highly dense filtered point cloud state as the main benefits a minor consumption of computational resources while obtaining a truly 3D analysis, less simplification of the reality, and the validation of the cause of obstruction with the original point cloud. On the other hand, those methodologies that make use of digital models claim that performing the calculations on the cloud might underestimate the ASD, since points that are not necessarily an obstruction could be wrongly considered as such [25]. Another disadvantage of methodologies performed directly on the cloud is their need for higher densities to avoid sightlines to pass through adjacent points resulting in overestimated values of ASD. Moreover, the literature showed that both digital surface models (DSMs) and digital terrain models (DTMs) have been properly used to evaluate sight distances exploiting Geographic Information Systems (GIS) tools [26,27]. Some authors favor the use of DSMs because they include information about the vegetation, edifications, and other elements around the road. However, one drawback of utilizing DSMs is that widespread formats only allow one elevation for each x and y position. Consequently, road settings cannot be represented three-dimensionally by using these formats. In this regard Iglesias Martinez et al. [28] presented a methodology of ASD estimation that makes use of multipatch datasets to represent road obstructions in addition to the terrain model. Most of the studies analyzed were developed for road segments, which require sight distances that are different to those of intersections. In 2017, Jung et al. [23] presented a procedure aimed specifically at the evaluation of required intersection sight distances. However, their methodology was cloud-based, which brings difficulties to the modelling and relocation of road assets, needed to evaluate the impact of their position on visibility.

3. Materials and Methods This research introduces a novel method aimed at improving the safety of VRUs. This procedure enables the comprehensive evaluation of VRUs visibility and the analysis of locations that could encourage unlawful road crossing. Initial steps are simplified in Figure2. Firstly, depending on the type of intersection (three leg, four leg, multi leg or roundabout), the required sight distances (RSD) are determined. Secondly, the ASD is obtained making use of a fully 3D methodology. After obtaining the ASD values, a comparison with the RSD is carried out in order to assess how much visibility VRUs have to perform certain maneuvers, and to verify that their reciprocal visibility with motorized traffic is provisioned at adequate distances. The required sight distances are the SSD and the ISD. In those sections where sight distances requirements are not met, an extra step is carried out so as to determine the nature of the obstructing elements. If the obstructing element belongs to vegetation, pertinent solutions are proposed. If the obstructing element belongs to street furniture or road assets whose functioning is location-related, an evaluation of their repositioning is performed so as to find their optimal location in terms of visibility. On the other hand, if the obstructing element is the road geometry itself, an examination of historical conflicts or accidents near the location is proposed, in order to evaluate if troublesome geometry modifications or speed changes are truly required. Afterwards, origin and destination points of interest (POIs) are identified within the functional area of the intersection. The routes from origin POI to destination POI are obtained using the dedicated pedestrian facilities and another route is obtained through the shortest path. When the difference between proper crossing and the shortest path is significant, a visibility evaluation around destination and origin POIs is carried out. Lastly, corrective measures are suggested. All these steps are described in more detail in later parts of the section. Sustainability 2019, 11, x FOR PEER REVIEW 5 of 16

SustainabilityLastly,2019 corrective, 11, 6630 measures are suggested. All these steps are described in more detail in later5 of 16 parts of the section.

Figure 2. DepictionDepiction of of the the first ﬁrst steps steps of of the the procedure. procedure.

3.1.3.1. Obtention of Required Sight Distances (RSD) (RSD) TheThe aspectsaspects of sight distances discussed herein herein are are those those needed needed to to ensure ensure safe safe intersection intersection functioning.functioning. These These are are the the sight sight distances distances needed needed for for stopping stopping (SSD) (SSD )and and to to enter enter and and exit exit the the intersectionintersection safelysafely (ISD). (ISD). The The formulations formulations of the of latterthe latter might might vary depending vary depending on the type on ofthe intersection type of underintersection study under and the study geometric and the design geometric guideline design utilized. guideline All sightutilized. distances All sight considered distances were considered obtained inwere consistency obtained within consistency the expressions with the provided expressions by the provided American by the Association American of Association State Highway of State and TransportationHighway and Transportation Officials (AASHTO) Officials [12 (AASHTO)]. [12]. SSDsSSDs areare necessarynecessary on all roads and streets. streets. These These were were calculated calculated with with Equations Equations (1) (1) and and (2). (2). TheThe firstfirst oneone considersconsiders the eeffectsffects of the grade, while the second one one does does not: not: 𝑉 V2 𝑆𝑆𝐷SSD = 0.278 = 0.278Vt + 𝑉𝑡 𝑎 (1)(1) 245 𝐺 245 [9.81a G ] 9.81 ± 𝑉 𝑆𝑆𝐷 = 0.278 𝑉𝑡 0.039 V2 (2) SSD = 0.278 Vt + 0.039 𝑎 (2) a where V is the design speed, t is the brake reaction time of 2.5 s (for drivers, riders and cyclists), 𝑎 is where V is the design speed, t is the brake reaction time of 2.5 s (for drivers, riders and cyclists), a is the the deceleration rate of 3.4 m/s for vehicles and 2.4 m/s for cyclists and riders, and G is the grade. deceleration rate of 3.4 m/s for vehicles and 2.4 m/s for cyclists and riders, and G is the grade. The intersection sight distance (ISD) is defined as that distance a driver has for, effectively and securely,The intersectionperceiving and sight reacting distance to (ISD) conflicting is defined trajectories, as that distancewithout ahaving driver the has right for, e ffofectively way [29]. and securely,Clear sight perceiving triangles that and provide reacting a to free conflicting view of the trajectories, entire intersection without are having essential. the right These of triangles way [29 ]. Clearare defined sight triangles for approach that provide and for a freedeparture. view of The the entirelength intersection of the triangles are essential. varies Thesewith the triangles type of are definedintersection, for approach the type andof intersection for departure. control The used length (no of control, the triangles stop control, varies withyield thecontrol, type traffic of intersection, signal, theall way type stop of intersection control, left controlturns or usedroundabouts), (no control, and stop depend control, on which yield road control, the control traffic signal,is established all way stop(minor control, or major). left turns or roundabouts), and depend on which road the control is established (minor or major).For roundabouts, two approaches are to be verified for each entry, the first with the vehicles circulatingFor roundabouts, and the second two approachesfor those entering. are to beTh verifiedese stream for distances each entry, were the verified first with according the vehicles to circulating and the second for those entering. These stream distances were verified according to Sustainability 2019, 11, 6630 6 of 16

Equations (3) and (4), d1 is the length of the entering leg of the sight triangle and d2 is the length of the circulating one [29]. d1 = 0.278 Vetc (3)

d2 = 0.278 Vctc (4) where Ve is the design speed of the entering stream, Vc is the design speed of the circulating stream, and tc is the critical headway for entering the major road with a value of 5 s for drivers, riders, and cyclists in both equations. Pedestrians do not have standard established formulae to obtain the sight distances they require to perform common maneuvers [30]. Since the crossing maneuver is the one with more fatalities among pedestrians, only their roadway crossing was taken into account. The crossing maneuver is considered to be complex and dependent on diﬀerent human and infrastructure related factors [31]. In this sense, this procedure focuses on those aspects associated with the geometry of the road and roadside elements. As pedestrians do not have RSD, their sightlines were not compared with their own requirements but with the SSD of drivers and riders. In summary, when evaluating the visibility of riders and cyclists, their required SSD and ISD are calculated so as to be compared with their ASD. For pedestrians, only their reciprocal visibility with other road users, at adequate distances, is ensured. This is done by comparing their ASD with the RSD of other road users. Drivers are the road users that imply higher harm to VRUs, therefore, an estimation of their stopping and intersection sight distances is useful to evaluate their capability to spot non-motorized users. These RSD ought to be analyzed for all the possible turns of those intersections under evaluation.

3.2. Procedure to Obtain ASD Road design guidelines also specify the criteria to measure or obtain the ASD. Measuring the ASD requires the definition of the object or target towards whom the sightline will be launched. This target depends on the RSD to be evaluated. For instance, SSD calculations consider as a target an object placed on the observer’s path. The height of this object depends on the observer analyzed (driver, rider or cyclist). On the other hand, ISD calculations consider a specified road user as the object to be seen. This means that SSD estimations, with a driver as an observer, consider an object/ target of 0.6 m height; if the observer is a cyclist or a rider the object height is 0 m. ISD evaluations considering a driver as a target require an object height of 1.08 m (the eye height of a driver). Thus, the considered target height of ISD estimations varies with the road user regarded as target. Another important aspect specified in the guidelines is the eye height and placement of the considered observers. These are summarized in Table1. Driver and cyclist values are in consistency with the specifications provided by the AASHTO [12,32].

Table 1. Eye height and placement of observers to be evaluated.

Observer Eye Height (m) Placement in the Road Scene Mobility impaired pedestrian 1.15 Center of the sidewalk Pedestrian 1.70 Center of the sidewalk Cyclist sharing the lane 1.40 1 m apart from the center of the lane Cyclist along riding facility 1.40 Center of their lane E-scooter rider sharing the lane 1.80 Center of the lane E-scooter along riding facility 1.80 Center of their lane Driver 1.08 Center of the roadway

These evaluations could be performed directly on the ﬁeld, or virtually on plans or proﬁles, or by making use of detailed representations of the road scene. An additional contribution of this study is a procedure that allows to obtain the ASD of intersections utilizing digital models. Sustainability 2019, 11, 6630 7 of 16

The ASDs are obtained by making use of geospatial data and GIS tools. As described by Iglesias-Martinez et al. [28], this procedure makes use of geospatial analysis functionalities from the ArcGIS software (Esri, Redlands, CA, USA), mainly the tools: Line Of Sight and Construct Sight Line. On the basis of these and other functionalities, a geoprocessing model was built utilizing the ModelBuilder application, also from ArcGIS. Data required to implement the procedure encompass the observer’s trajectory, the digital model, and optionally 3D objects standing as potential obstructions. This methodology was originally meant to perform evaluations of SSD on road segments. The evaluation of SSD on road segments considers the observer and target to be along the same trajectory. Intersections, on the other hand, require the projection of lines-of-sight from observers to targets that belong not only to their own path but also to conflicting trajectories and conflicting points that could be placed in distinct parts of the roadway or even out of it. Due to these facts, a modification of the queries involved in the selection of the sightlines was done, so as to adapt it to the requirements of intersections. In addition to that, the assessments presented herein not only include the roadway but also cycle paths, cycle routes and adjacent sidewalks, when present. Data required as input are described in the following lines. Trajectories are required to place the successive positionings of the considered observers. Table1 showed the considered eye height for each observer as well as their placement. As mentioned, main observers are pedestrians with mobility impairments and without them, cyclists and personal transportation device riders. Each of these users travel in differentiated areas of the road scene. This analysis considers the eye height as the only differentiating factor between mobility impaired pedestrians and those who are not. Cyclists were considered to be sharing the roadway as well as using cycling facilities. When evaluated as sharing the roadway, two trajectories were depicted from the center of the lane. This is done owing to their meandering trajectory, for which they could occupy almost any position of the lane. Electrical scooter riders were considered to be sharing the roadway. Due to the fact that these devices require fewer meandering movements than bikes, these observers were only located in the center of their lanes. All these trajectories could be digitized from exiting cartography, obtained from official sources of geospatial data or from voluntary geographic information projects. Additionally, real trajectories of shared mobility services ran by city councils are often available in widespread formats. Trajectories were then discretized into a set of equally spaced stations. For drivers, cyclists, and riders the separation between points was 5 m. Pedestrians were represented by equally separated stations of 1 m, this separation considers the average pedestrian stride and common wheelchair measurements. The digital terrain model and the aboveground obstructions could be obtained from highly accurate, high resolution geospatial data. Data employed to perform the evaluations were obtained from LiDAR based mobile mapping systems (MMS). Figure3 shows the main processing steps required by the point cloud in order to deliver the DTM and the 3D objects. The point cloud was firstly referenced to the desired coordinate reference system. Subsequently, points that were the product of abnormal measurements or dynamic objects were removed. After this denoising, points were classified according to the element they belong to. These classes could be ground, edification, road utility, high vegetation, medium vegetation, noise and so forth. Depending on their classification, they were used to make one model or the other. The DTM representing the ground and road geometry as well as the 3D objects depicting aboveground obstructions ought to be precise enough to allow realistic measurements to be carried out. Data were obtained from the terrestrial Laser Scaner, Leica C10 and from the MMS IPS3 from Topcon [33,34]. Both surveys were planned and compiled to meet approximately 10 mm horizontal ± and 15 mm vertical accuracy at 95% confidence level. The resulting point clouds were pre-processed ± with software provided by each of the vendors. The projecting, denoising, classification, and filtering of the cloud was performed in-house with the software MDTOPx [35]. SustainabilitySustainability2019 2019, ,11 11,, 6630 x FOR PEER REVIEW 88 of of 16 16

Sustainability 2019, 11, x FOR PEER REVIEW 8 of 16

Figure 3. Processing required by the point cloud in order to deliver the required data. Figure 3. Processing required by the point cloud in order to deliver the required data. The DTM was generated with those points classified as ground. These models could be stored in AbovegroundFigure 3. Processingobstructions, required such by as the vegetation, point cloud roadin order assets, to deliver street the furniture, required data. and manmade raster or vector formats. edifications were included in the evaluation as 3D objects. This was done by making use of the AbovegroundAboveground obstructions,obstructions, such asas vegetation,vegetation, roadroad assets,assets, streetstreet furniture,furniture, andand manmademanmade multipatch format created by ESRI [36]. These files allow to portray the outer surface of three- edificationsedifications were included in in the the evaluation evaluation as as 3D 3D objects. objects. This This was was done done by bymaking making use useof the of dimensional features. Other considered 3D features were modelled utilizing the software SketchUp themultipatch multipatch format format created created by ES byRI ESRI [36]. [36These]. Thesefiles allow files allowto portray to portray the outer the outersurface surface of three- of [37] or obtained from online libraries and imported into the model. three-dimensionaldimensional features. features. Other considered Other considered 3D features 3D featureswere modelled were modelled utilizing the utilizing software the SketchUp software Figure 4 shows one of the DTMs utilized (yellowish element) with the multipatch file depicting SketchUp[37] or obtained [37] or from obtained online from libraries online and libraries imported and importedinto the model. into the model. the vegetation on top (green element) and a 3D object representing the bus stop is shown in blue. FigureFigure4 4 shows shows one one of of the the DTMs DTMs utilized utilized (yellowish (yellowish element) element) with with the the multipatch multipatch file file depicting depicting thethe vegetationvegetation onon toptop (green(green element)element) andand aa 3D3D objectobject representingrepresentingthe the bus bus stop stop is is shown shown in in blue. blue.

Figure 4. Road section depicted with a digital terrain model and aboveground elements as a multipatch files. FigureFigure 4.4. RoadRoad section section depicted depicted with a digital terrain model and abovegroundaboveground elementselements asas aa multipatchmultipatchAll these ﬁles.files.inputs allowed the virtual launching of sightlines repeatedly from each observer’s location to the designated target. Results from this model are the ASD values for each observer, the AllAll thesethese inputsinputs allowedallowed thethe virtualvirtual launchinglaunching ofof sightlinessightlines repeatedlyrepeatedly fromfrom eacheach observer’sobserver’s polyline describing the trajectory of the unobstructed sightline from observer to target, and a point locationlocation to the designated designated target. target. Results Results from from this this model model are are the the ASD ASD values values for foreach each observer, observer, the feature with the exact coordinates of the objects that caused disruptions to the visuals. thepolyline polyline describing describing the the trajectory trajectory of ofthe the unobstruct unobstructeded sightline sightline from from observer observer to to target, target, and a pointpoint featurefeature withwith thethe exactexact coordinatescoordinates ofof thethe objectsobjects thatthat causedcaused disruptionsdisruptions to to the the visuals. visuals. 3.3. Location and Categorization of Obstructions

3.3.3.3. LocationBy analyzing and CategorizationCatego the resultsrization obtained ofof ObstructionsObstructions from the model it was possible to determine the exact location where the line of sight got interrupted, and thus, determine the cause of obstruction (whether from ByBy analyzinganalyzing thethe resultsresults obtainedobtained fromfrom thethe modelmodel itit waswas possiblepossible toto determinedetermine thethe exactexact locationlocation the aboveground feature depicted as a 3D object, or the topography or road geometry element wherewhere thethe line line of of sight sight got got interrupted, interrupted, and and thus, thus, determine determine the the cause cause of obstructionof obstruction (whether (whether from from the represented by the DTM). If the obstruction is caused by overgrown vegetation, street furniture or abovegroundthe aboveground feature feature depicted depicted as a 3D as object, a 3D or object, the topography or the topography or road geometry or road element geometry represented element road assets whose functioning do not depend on their location (benches, garbage bins, etc.), pertinent byrepresented the DTM). by If the the DTM). obstruction If the isobstruction caused by is overgrown caused by vegetation,overgrown streetvegetation, furniture street or furniture road assets or solutions are evaluated, such as improving vegetation management or asset relocation, and no road assets whose functioning do not depend on their location (benches, garbage bins, etc.), pertinent solutions are evaluated, such as improving vegetation management or asset relocation, and no Sustainability 2019, 11, 6630 9 of 16

whoseSustainability functioning 2019, 11, dox FOR not PEER depend REVIEW on their location (benches, garbage bins, etc.), pertinent solutions9 of are16 evaluated, such as improving vegetation management or asset relocation, and no further processing is done.further Other processing road assets is done. or Other street road furniture assets whose or street functioning furniture whose are location-based functioning are (bus location-based stops, traffic signs,(bus stops, traffic traffic lights) signs, are modelled traffic lights) as 3D are objects modelled and as displaced 3D objects around and displaced their original around location, their original so as to evaluatelocation, the so impactas to evaluate of their the relocation. impact of The their digital relocation. representation The digital of theserepresen elementstation of could these be elements obtained directlycould be from obtained the point directly cloud, from and the in the point case cloud, of not and having in the enough case of resolution not having tomodel enough them resolution accurately, to manymodel street them assets accurately, with fixed many dimensions street assets were with already fixed modeled dimensions and were stored already in different modeled collaborative and stored 3D designin different software collaborative warehouses. 3D Thedesign real software elements wareho could beuses. easily The deleted real elements from the could models be easily and relocated. deleted Figurefrom the5 presents models and a modeled relocated. bus Figure stop 5 shelter presents that a modeled required bus few stop editing shelter tasks, that required so as to representfew editing a realtasks, element. so as to represent a real element.

FigureFigure 5. 5.3D 3D objectobject representingrepresenting aa busbus stopstop sheltershelter next to a similar bus stop obtained obtained from from Google Google StreetStreet View View [ 38[38].].

3.4.3.4. Identification Identification ofof PointsPoints ofof InterestInterest andand Jaywalking-ProneJaywalking-Prone Locations AsAs abovementioned,abovementioned, thethe complexitycomplexity of urban settings relies relies also also in in their their high high number number of of destinations.destinations. TheThe majority of edifications edifications and and elem elementsents located located near near urban urban intersections intersections represent represent a aPOI POI for for a auser user or or a agroup group of of users. users. This This means means that that almost almost every every point point requires requires a proper a proper access. access. In Inthis this sense, sense, this this analysis analysis only only considers considers as as origin origin POIs POIs edifications edifications with with high high occupancy occupancy (universities, (universities, ooffice’sffice’s buildings, buildings, shoppingshopping malls).malls). POIs considered as destinations were were transportation transportation facilities, facilities, suchsuch as as elements elements of of the the publicpublic transit,transit, parkingparking lots,lots, and spots with agglomeration of of micro-mobility micro-mobility solutionssolutions (bike (bike share, share, mopedmoped andand e-scootere-scooter parking,parking, etc.).etc.). Having identified identified the the POIs POIs located located inside inside thethe intersection’s intersection’s functionalfunctional area,area, aa measurementmeasurement of the distance between between the the origin origin POI POI and and the the destinationdestination POIPOI isis made.made. First, First, a a route route using using thei theirr dedicated dedicated crossings crossings is iscreated created and and after after that, that, a asecond second path path through through the the shortest shortest possible possible route route is is also also generated. If If the the distance distance utilizing utilizing the the pedestrianpedestrian facilities facilities properly properly isis tootoo longlong compared withwith the second second one, one, sight sight distances distances are are evaluated. evaluated. ThisThis evaluation evaluation considers considers motorizedmotorized tratrafficffic asas observersobservers and pedestrians as targets. targets. The The targets targets were were placedplaced along along the the sidewalksidewalk andand inin middlemiddle streetstreet locationslocations (as if they were unlawfully crossing) crossing) near near thethe POIs. POIs. This This assessmentassessment verifiesverifies fromfrom whichwhich distancesdistances drivers cruising at at the the posted posted speed speed limit limit are are capablecapable of of seeing seeing unexpected unexpected pedestrians.pedestrians. AsAs with with the the trajectories, trajectories, informationinformation regarding POIs could be obtained from from official official sources sources of of geospatialgeospatial data data or or from from voluntary voluntary geographicgeographic informationinformation projects.projects.

4.4. Results Results DistinctDistinct types types of urbanof urban intersections intersections were were mapped mapped utilizing utilizing diﬀerent different MMS services. MMS services. The following The sectionfollowing shows section the mainshows ﬁndings the main of thefindings evaluations of the performedevaluations applyingperformed the applying procedure, the explainedprocedure, in theexplained previous in section,the previous to two section, urban to intersections, two urban in atersections, T-junction anda T-junction a roundabout. and a roundabout. These assessments These consideredassessments all considered their possible all turns their and possible all the turns observers and previouslyall the observers listed. Nearlypreviously a hundred listed. casesNearly were a run.hundred All evaluations cases were had run. their All evalSSDuationsand ISD had examined their SSD but and their ISD results examined are shownbut their separately. results are Each shown one separately. Each one of the cases listed below is defined by the road user considered as main observer, and the user/object considered as target; the type of required distance analyzed (stopping or intersection), and the type of intersection selected. The movement under analysis (turn left from Sustainability 2019, 11, 6630 10 of 16

Sustainability 2019, 11, x FOR PEER REVIEW 10 of 16 of the cases listed below is deﬁned by the road user considered as main observer, and the user/object consideredminor road as to target; major, the turn type right of requiredfrom major distance road, analyzedpedestrian (stopping crossing, or etc.) intersection), is also described and the for type each of intersectioncase. selected. The movement under analysis (turn left from minor road to major, turn right from major road, pedestrian crossing, etc.) is also described for each case. 4.1. Visibility at a Stop-Controlled T-Junction (Mobility Impaired Pedestrian crossing) 4.1. Visibility at a Stop-Controlled T-Junction (Mobility Impaired Pedestrian crossing) This evaluation was carried out in a three-way, signalized, skewed intersection located in the city ofThis Madrid, evaluation whose was geometry carried outdescription in a three-way, is shown signalized, in Figure skewed 6. These intersection roads feature located grades in theof 5.3% city of(main Madrid, road) whose and 4.2% geometry (minor description road). Mobility is shown impaired in Figure pedestrians6. These roads were feature considered grades to of 5.3%be the (main main road)observers. and 4.2% (minor road). Mobility impaired pedestrians were considered to be the main observers.

FigureFigure 6.6. GeneralGeneral depictiondepiction ofof thethe junctionjunction underunder study.study.

Observers were located in the center of the sidewalk with an eye height of 1.15 m, as speciﬁed Observers were located in the center of the sidewalk with an eye height of 1.15 m, as specified in Table1. Drivers and cyclists were the road users considered as main targets and towards whom in Table 1. Drivers and cyclists were the road users considered as main targets and towards whom the sightlines were launched. Additionally, their RSDs were the ones compared with the ASD of the the sightlines were launched. Additionally, their RSDs were the ones compared with the ASD of the pedestrians. As this intersection lacks cyclists’ facilities, these riders were considered to be sharing the pedestrians. As this intersection lacks cyclists’ facilities, these riders were considered to be sharing lane. Required SSD for drivers and riders (facing traﬃc) are displayed in Table2. the lane. Required SSD for drivers and riders (facing traffic) are displayed in Table 2.

Table 2. Required stopping sight distances for cyclists along the intersection. Table 2. Required stopping sight distances for cyclists along the intersection. SSD (m) Downward SSD (m) Upward SSD (m) Downward TargetsSSD (m) Downward Main SSD (m) Upward Minor SSD (m) Downward Minor Targets Main Road Minor Road Minor Road Road Road Road Cyclists 40.75 36.74 40.16 Cyclists 40.75 36.74 40.16 Drivers Drivers49.30 49.30 44.01 44.01 48.48 48.48

FigureFigure7 shows7 shows selected selected sightlines sightlines towards towards the minor the road.minor For road. description For description purposes, thepurposes, pedestrian the ispedestrian considered is to goconsidered from west to to east.go from The first west pedestrian to east. crossing The first encounters pedestrian drivers crossing/riders downwardsencounters fromdrivers/riders the minor downwards road, here observers from the areminor provisioned road, here with observers more thanare provisioned 50 m of clear with sights more uphill than along 50 m theof clear roadway. sights This uphill was along estimated the roadway. for both ends This ofwas the estimated crossing, forfor allboth targets. ends Theof the second crossing, pedestrian for all crossingtargets. The provides, second in pedestrian its first end, crossing sufficient provides, visibility in it ofs first traffi end,c upwards sufficient the visibility minor road.of traffic The upwards second endthe ofminor this crossing,road. The however, second end showed of this restricted crossing, sight however, distances. showed Here therestricted sightlines sight towards distances. the mainHere roadthe sightlines were obstructed towards by the a bus main stop-shelter road were located obstructed 35 m from by a the bus intersection. stop-shelter Pedestrians located 35 goingm from down the theintersection. main road Pedestrians must look backgoing for down oncoming the main vehicles, road must which look is usually back for done oncoming fast and vehicles, not carefully. which is usually done fast and not carefully. Sustainability 2019, 11, 6630 11 of 16 Sustainability 2019,, 11,, xx FORFOR PEERPEER REVIEWREVIEW 11 of 16

FigureFigure 7. 7.Sightlines Sightlines of pedestrians of pedestrians crossing crossing the minor the road. minor Purple road. dots Purple describe dots pedestrians describe positioningpedestrians andpositioning red dots areand drivers red dots going are drivers down the going minor down road. the minor road.

DueDue to to the the fact fact that that the the location location of of the the bus bus stop stop serves serves a a purpose, purpose, an an evaluation evaluation of of its its relocation relocation waswas performed. performed. This This evaluation evaluation was was carried carried out out two two more more times: times: the the first first one one without without bus bus stop-shelter stop-shelter andand the the second second one one with with the the bus bus stop-shelter stop-shelter located located 5 5 m m uphill uphill from from its its real real location. location. In In addition addition to to thethe evaluation evaluation of of the the visibility visibility of pedestrians, of pedestrians, the assessment the assessment of the ofSSD theand SSD ISD and of driversISD of anddrivers cyclists and wascyclists also runwaswith also therun newwith locations the new locations of the bus of stop. the bus Pedestrians stop. Pedestrians were provisioned were provisioned adequately adequately with the 5with m relocation. the 5 m relocation. Furthermore, Furthermore, the RSDs ofthe drivers RSDs of for dr thisivers turn for was thisfound turn was to be found satisfied to be by satisfied the ASD by andthethere ASD were and nothere relevant weree noffects relevant from the effects bus stop. from Sightlines the bus stop. projected Sightlines from cyclists projected considered from cyclists to be ridingconsidered near the to be curb riding turned near out the to curb be blocked turned out by theto be bus blocked stop shelter by the (Figurebus stop8). sheltershelter After (Figure the(Figure relocation, 8).8). AfterAfter atthe distances relocation, of 50 at m distances uphill the of main 50 m road, uphill these the riders main were road, capable these ofriders properly were spotting capable pedestrians of properly aboutspotting to cross pedestrians and those about already to cross crossing. and those already crossing.

FigureFigure 8. 8.Available Available sight sight distance distance for afor stopping a stopping maneuver maneuver of cyclists of cyclists riding near riding the near curb. the Gray curb. features Gray arefeatures the multipatch are the multipatch ﬁles as vegetation files as vegetation and the 3D and element the 3D depicting element thedepicting bus stop the is bus presented stop is inpresented white. inin white.white. 4.2. SSD of Cyclists at a Stop-Controlled T-Junction 4.2. TheSSD considered of Cyclists at junction a Stop-Controlled is the same T-Junction as described above. The movement evaluated is the right turn fromThe theconsidered minor road. junction Observers is the same were as considered described to above.above. be cyclists TheThe movementmovement and the target evaluatedevaluated was an isis object thethe rightright of heightturn from 0.15m. the Figure minor9 showsroad. Observers the results were of the considered evaluation; to Figure be cyclists9a depicts and the the considered target was trajectories an object of eachheight 1 m 0.15 apart m. from Figure the 9 center shows of the laneresults and of with the anevaluation; equal separation Figure 9a of 5depicts m. Figure the 9consideredb shows thetrajectories sight distance each 1 chart m apart of both from trajectories. the center of The the graph lane and displays with an the equal distances separation along of the 5 roadm. Figure on the 9b horizontalshows the axis sight and distance the sight chart distances of both on trajectories the vertical.. TheThe one. graphgraph Constant displaysdisplays reductions thethe distancesdistances in the alongalong ASD arethethe dueroadroad toon the the horizontal horizontal curve. axis and However, the sight the distances ASD do on not th takee vertical values one. that Constant are lower reductions than the requiredin the ASDSSD are. due to the horizontal curve. However, the ASD do not take values that are lower than the required Sustainability 2019, 11, 6630 12 of 16 Sustainability 2019, 11, x FOR PEER REVIEW 12 of 16 Sustainability 2019, 11, x FOR PEER REVIEW 12 of 16 Generally speaking, both trajectories show the same tendency, but diﬀerences of 5 and even 10 m of SSD.SSD. Generally Generally speaking,speaking, both trajectories show thethe samesame tendency,tendency, but but differences differences of of 5 5 and and even even 10 10 visibility arise at some stations. mm of of visibility visibility arisearise atat somesome stations.

((a)) (b(b) ) Figure 9. Sight distance for a stopping maneuver along the minor road. (a) Depiction of cyclists FigureFigure 9.9. SightSight distance for a stopping maneuver along the the minor road. road. (a (a) )Depiction Depiction of of cyclists cyclists positioning, (b) comparison of sight distances for both cyclists. positioning,positioning, ((bb)) comparisoncomparison ofof sightsight distancesdistances for both cyclists.

4.3.4.3. SSD SSD ofof ElectricElectric Scooter Scooter Riders and Cyclists at a a RoundaboutRoundabout ThisThis evaluationevaluation was was carried out in a two-lane roundaboutroundabout withwith threethree three entriesentries and and and two two two exits. exits. exits. FigureFigure 1010 displaysdisplays aa depictiondepictiondepiction ofof itsits geometry.geometry. Th ThisThisis roundaboutroundabout contains containscontains a aa non-mountable non-mountablenon-mountable central centralcentral islandisland ofof approximatelyapproximately 2525 mm diameter,diameter, oneone raisedraised splitter splitter island, island,island, and andand two twotwo painted. painted.painted. The The minor minor road road meetsmeets its itsits end endend in inin the thethe roundabout, roundabout,roundabout, with with an approachan approach width widthwidth of 5.5 ofof m 5.55.5 and mm entry andand entry widthentry width ofwidth 6.3 m.of of 6.3 No6.3 m. refugesm. No No arerefugesrefuges present are are at presentpresent its straight atat itsitspedestrian straightstraight pedestrian crossings, crossings, which are whichwhich located areare 16 located located and 24 m16 16 awayand and 24 24 from m m away away the entries from from /theexit. the Observersentries/exit.entries/exit. were ObserversObservers considered werewere to considered be cyclists andto be riders cyclists whose andand targetridersriders waswhose whose an target objecttarget was of was height an an object object 0.15 m.of of height Tableheight3 shows0.150.15 m. m. the Table Table required 33 showsshowsSSD thetheof required these users. SSD of these users.users.

Figure 10. General depiction of the junction under study. Figure 10. General depiction of the junction under study. Table 3. Required stopping sight distance along the intersection. Table 3. Required stopping sight distance along the intersection. Table 3. Required stopping sight distance along the intersection. ObserverObserver SSD (m)SSD (m) Observer SSD (m) E-scooterE-scooter rider rider (30 (30 km/h) km/h) 35.5 35.5 E-scooter rider (30 km/h) 35.5 CyclistCyclist (30 (30km/h) km/ h) 35.5 35.5 Cyclist (30 km/h) 35.5 Sustainability 2019, 11, 6630 13 of 16

Sustainability 2019, 11, x FOR PEER REVIEW 13 of 16 The evaluated turn considered observers to be downward the main road. Due to the fact that this roundaboutThe containsevaluated a turn cycle considered track and observers an oﬀ-street to be bike downward pathway, the cyclists main road. were Due not onlyto the considered fact that to be sharingthis roundabout the lane butcontains alsoplaced a cycle in track their and dedicated an off-street infrastructure. bike pathway, However, cyclists results were presented not only here considered to be sharing the lane but also placed in their dedicated infrastructure. However, results are the ones obtained from their evaluations on the roadway. Figure 11 shows their lane positioning presented here are the ones obtained from their evaluations on the roadway. Figure 11 shows their (11a) next to their resulting sight chart (11b). lane positioning (11a) next to their resulting sight chart (11b).

(a) (b)

FigureFigure 11. 11.(a) (a Stationing) Stationing ofof cyclists cyclists and and riders riders along along the major the majorroad, (b road,) comparison (b) comparison of their sight of their distances. sight distances.

As shownAs shown in Figurein Figure 11 a,11a, all all users users were were considered considered to to be be on on the the same same lane.lane. FigureFigure 1111bb exposes the the variations of the ASD along the roundabout. Initially, ASD values of all observers show a constant variations of the ASD along the roundabout. Initially, ASD values of all observers show a constant decrease. Around stations 120, and up to station 145, all users had ASD values that were lower than decrease. Around stations 120, and up to station 145, all users had ASD values that were lower than the required SSD, and after a local increase another decrease caused the ASD to not meet the required the requiredSSD, this timeSSD ,at and around after stations a local increase175 and up another to 205. decrease These minimums caused the were ASD caused to not by meet the entry the requiredand SSDexit, this radios time of at the around roundabout. stations The 175 small and variations up to 205. on Thesethe ASD minimums of all observer weres were caused due by to the effects entry and exitof radios vegetation of the and roundabout. its distinctive The impact small variations on each user. on theThe ASD approach of all sight observers distance were was due confirmed, to the eff ects of vegetationobservers were and able its distinctive to spot the impactyield line on and each cro user.sswalks The from approach distances sight superior distance to their was required confirmed, observersSSD. The were approach able to entry spot and the the yield surrounding line and vegeta crosswalkstion prevented from distances these observers superior from totheir efficiently required SSDspotting. The approach traffic along entry the and minor the road. surrounding vegetation prevented these observers from efficiently spotting traffic along the minor road. 4.4. Evaluation of a Jaywalking Prone Location at a Roundabout 4.4. EvaluationThis evaluation of a Jaywalking was performed Prone Location on the roundabout at a Roundabout described above. This junction is located near officesThis evaluationand educational was performedbuildings that on thewere roundabout considered describedto be the origin above. POIs. This The junction destination is located POIs near officeswere and bus educational stops near these buildings buildings. that Pedestrians were considered usually to rush be thearound origin bus POIs. stops Theand destinationthis behavior POIs could impose risks on their safety. Most buildings located within the functional area of the were bus stops near these buildings. Pedestrians usually rush around bus stops and this behavior intersection were well communicated to near bus stops using the crosswalks. Only one educational could impose risks on their safety. Most buildings located within the functional area of the intersection building, shown in Figure 12, demanded VRUs to travel a distance of 400 m utilizing all the required werepedestrian well communicated crossings and to200 near m jaywalking bus stops around using th thee roundabout. crosswalks. An Only evaluation one educational of the visibility building, of shownfacing in Figuretraffic was 12, demandedperformed towards VRUs to the travel road asect distanceion and of sidewalk 400 m utilizing near the allbus the stop. required The observers pedestrian crossingswere drivers and 200 and m the jaywalking targets were around pedestrians. the roundabout. Drivers traveling An evaluation at the posted of the speed visibility limit of of facing40 km/h tra ffic wasrequired performed 46.2 towards m to perform the road an sectionadequate and stop. sidewalk Figure 12 near shows the busthe stop.results The of this observers evaluation. were The drivers andorigin the targets POI is highlighted were pedestrians. by a red circle Drivers and travelingthe bus stop at with the postedan icon. speedResults limit shown of for 40 this km /specifich required 46.2evaluation m to perform were anthe adequate points where stop. the Figure visuals 12 got shows obstructed, the results these ofpoints this are evaluation. shown in TheFigure origin 12 and POI is highlightedcolored in by red. a red For circle illustration and the purposes, bus stop an with interrupted an icon. sightline Results 90 shown m away for from this specificthe bus evaluationstop is weredisplayed, the points this where station the and visuals stations got nearby obstructed, had their thesesightlines points obstructed, are shown the green in Figure part is12 the and visible colored in red.part For and illustration the red one purposes, is the obstructed an interrupted part. The sightline vegetation 90 and m away the abutting from the fence bus were stop the is displayed, main visual obstructions. Results also show that drivers located 60 m away from the bus stop were not able this station and stations nearby had their sightlines obstructed, the green part is the visible part and the to spot pedestrians starting to cross. This would come as a surprise to these drivers who could be red one is the obstructed part. The vegetation and the abutting fence were the main visual obstructions. focused on the incoming traffic from the exit of the roundabout. Results also show that drivers located 60 m away from the bus stop were not able to spot pedestrians starting to cross. This would come as a surprise to these drivers who could be focused on the incoming traffic from the exit of the roundabout. Sustainability 2019, 11, 6630 14 of 16 Sustainability 2019, 11, x FOR PEER REVIEW 14 of 16

FigureFigure 12. 12.Results Results of of the the valuationvaluation of a jaywalking-pronelocation.

5. Discussion5. Discussion TheThe first first evaluation evaluation stressed stressed the impactthe impact that streetthat furniturestreet furniture and road and assets road has assets on thehas considered on the mobility-impairedconsidered mobility-impaired pedestrian. pedestrian. The presented The presen methodted allowedmethod allowed to evaluate to evaluate the influence the influence of the obstructingof the obstructing element onelement the observer’s on the observer’s visibility visibility and to assessand to theassess effects the ofeffects its relocation. of its relocation. This process This presentsprocess advantageous presents advantageous functionalities functionalities that could that helpcould the help management the management of urban of urban furniture furniture and roadand assets. road assets. ResultsResults of of the the second second evaluation evaluation exposed exposed thethe distinctivedistinctive effects effects vegetation vegetation had had on on the the considered considered trajectories.trajectories. Despite Despite the the fact fact that that the the observers observers werewere consideredconsidered to to be be in in the the same same lane lane and and only only two two meters apart from each other, cyclists’ ASDs showed differences of up to 10 m. As abovementioned, meters apart from each other, cyclists’ ASDs showed differences of up to 10 m. As abovementioned, different guidelines expose specific locations where to consider the trajectory of drivers when different guidelines expose specific locations where to consider the trajectory of drivers when calculating calculating the ASD. When it comes to riders, due to the fact that they could take almost any position the ASD. When it comes to riders, due to the fact that they could take almost any position in the lane, in the lane, evaluating only one possible trajectory could deliver misleading results. The same could evaluating only one possible trajectory could deliver misleading results. The same could be said about be said about electric scooter riders, whose presence continues to increase in the road scene. electricEvaluating scooter the riders, overall whose sight presencedistances continuesof these users to increase on existing in the roads road is fundamental, scene. Evaluating due to the the overall fact sightthat distances many cities of theseare fostering users on and existing encouraging roads mo is fundamental,re sustainable duemodes to theof transportation fact that many without cities a are fosteringproper andevaluation encouraging of how more these sustainableroads perform modes for VRUs. of transportation without a proper evaluation of how theseThe roads third performevaluation for VRUs.considered observers to be electric scooter riders and cyclists. This roundaboutThe thirdevaluation encompassed considered cycle paths observers and cycle to be routes electric. However, scooterriders cyclists and with cyclists. higher This expertise roundabout and encompassedconfidence tend cycle to paths share and the cycleroadway, routes. in spite However, of having cyclists a dedicated with higher infrastructure, expertise for and that confidence reason tendthe to trajectories share the roadway,of cyclists inwere spite also of evaluated having a dedicatedin the roadway, infrastructure, one meter for apart that from reason the thecenter trajectories of the of cyclistslane, as with were the also previous evaluated cases. in This the roadway,case showed one how meter these apart VRUs from didthe not centerhave enough of the lane,visibility aswith of thethe previous traffic approaching cases. This casethe minor showed road. how Visibility these VRUsrestrictions did not caused have by enough the entry visibility angle are of meant the tra toffi c approachingdiscourage the motorists minor road.from speeding, Visibility but restrictions in the case caused of VRUs by theit imposes entry angle a visibility are meant restriction. to discourage motoristsThe from evaluation speeding, of the but potential in the case jaywalking of VRUs location it imposes highlighted a visibility how restriction. urban furniture elements (theThe fence evaluation and vegetation) of the potential prevented jaywalking drivers to spot location pedestrians highlighted that were how un urbanlawfully furniture crossing. elements This (theevaluation fence and is founded vegetation) on the prevented premises driversthat users to wi spotll make pedestrians mistakes and that the were anticipation unlawfully of possible crossing. Thisconflicts evaluation and risk is founded locations onhelps the to premises ensure the that safe users road willoperation. make mistakes and the anticipation of possible conflicts and risk locations helps to ensure the safe road operation. 6. Conclusions 6. ConclusionsLack of visibility and inadequate sight distances are contributing factors to traffic accidents involving pedestrians. As other road users, pedestrians use the information they infer from the road Lack of visibility and inadequate sight distances are contributing factors to traffic accidents scene to make decisions about their crossing behavior. These decisions have direct impact on drivers involving pedestrians. As other road users, pedestrians use the information they infer from the and other users. Reciprocal visibility helps to avoid erratic operations and potential conflicts. Urban road scene to make decisions about their crossing behavior. These decisions have direct impact Sustainability 2019, 11, 6630 15 of 16 on drivers and other users. Reciprocal visibility helps to avoid erratic operations and potential conflicts. Urban intersections are particularly complex sections, due to their multiple users, movements, visual obstructions, and conflicting trajectories. On top of that, current transport trends have modified the way many users interact with the road, adding more challenges to the already existing ones. ASD estimations are helpful to obtain an insight into how these roads perform for VRUs sharing the road. This paper presents a procedure to assess safety aspects that are related to sight distances on existing roads. This three-dimensional evaluation permits to assess the effect of complex obstructions properly. Results evidence that this procedure is useful to make evaluations on distinct types of intersections and allows the consideration of different users. The flexibility of the method permits to evaluate the visibility of new road users. As future lines of research, the authors plan to take advantage of the interoperability provided by widespread GIS software and include in the analysis other factors related to pedestrian’s safety.

Author Contributions: Conceptualization, M.C. and K.G.-G.; methodology, M.C. and K.G.-G.; validation, K.G.-G.; formal analysis, M.C. and K.G.-G.; writing—original draft preparation, M.C. and K.G.-G.; supervision, M.C.; project administration, M.C.; funding acquisition, M.C. Funding: This research was funded by the Spanish Ministerio de Economía y Competitividad and the European Regional Development Fund (FEDER), grant number TRA2015-63579-R (MINECO/FEDER). Acknowledgments: The authors gratefully acknowledge the financial support of the Spanish Ministerio de Economía y Competitividad and European Regional Development Fund (FEDER). Research Project TRA2015-63579-R (MINECO/FEDER). Conflicts of Interest: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

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