Tramways in Urban Areas: an Overview on Safety at Road Intersections
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Urban Rail Transit (2018) 4(4):223–233 https://doi.org/10.1007/s40864-018-0093-5 http://www.urt.cn/ ORIGINAL RESEARCH PAPERS Tramways in Urban Areas: An Overview on Safety at Road Intersections Marco Guerrieri1 Received: 26 July 2018 / Revised: 26 November 2018 / Accepted: 4 December 2018 / Published online: 11 December 2018 Ó The Author(s) 2018 Abstract Although the accident number involving trams is 1 Introduction comparatively very limited to the total road accident number, the consequences of tram crashes are very serious, In order to ease traffic congestions and lower air pollution especially when pedestrians are run over. The new power levels in big cities, a lot of countries are increasingly supply technologies (e.g. catenary-free systems) allow to resorting to tramway systems, considered as environmen- build tram networks, even in old town centres and pedes- tally sustainable, reliable and able to meet high mobility trian areas, with additional increased risk of pedestrian demands [1]. The new ground-level power supply tech- casualties. This will require specific design solutions and nologies (e.g. APS by Alstom, TramWave by Ansaldo) and traffic regulations for road safety as described in this paper, the developing systems like the induction technique (e.g. with particular regard to vulnerable users (i.e. pedestrians Bombardier Primove) allow tramways to be perfectly and cyclists), especially near intersections and pedestrian compatible with old town centres from both architectural crossings. Therefore, the research analyses the road acci- and urban planning viewpoints, in that they are catenary- dent rate and its evolution in the last 10 years with specific free [2]. focus on Italian tramways. The main risk conditions and However, tramway accidents have been more frequent the strategies used worldwide to improve the safety of since incentive schemes have encouraged public transport tramway system in the urban context are described. The use. It is widely known that people underestimate the main countermeasures to reduce accident risks are aimed at probability of being involved in a negative event (e.g. road better warning road users of specific risk conditions. Other accidents, diseases, economic problems) during their life- countermeasures are designed to install suitable facilities time, in that they consider themselves to be somehow on road platforms for better informing users of tramway invulnerable: an attitude defined unrealistic optimism in system, for limiting or temporarily prohibiting turning psychology [3]. Consistent with this empirical evidence, movements or manoeuvrings and for properly channelling road users (pedestrians, motor/cyclists and motorists) pedestrian and vehicle flows with the purpose to avoid or underestimate the risk of meeting tramway accidents reduce interference with trams. because of low tram speed and careful tram drivers [4]. Moreover, risk perception is affected by user type and Keywords Tramway systems Á Road intersections Á Road age. It has been precisely observed that [5]: safety Á Urban context • young pedestrians (15*29 years old) perceive interac- tions with trams as globally riskier to themselves and the others than pedestrians of different ages; & Marco Guerrieri • young car drivers and cyclists (15*29 years old) are [email protected] unrealistically optimist and underestimate the accident 1 DICAM, University of Trento, Via Mesiano 77, risk. 38123 Trento, Italy Tramway systems, therefore, pose numerous prob- Communicated by Xuesong Zhou. lems—to some extent still unsolved—on road safety and 123 224 Urban Rail Transit (2018) 4(4):223–233 protection of the socalled vulnerable users (e.g. cyclists, In addition to conventional catenary-fed trams, new pedestrians, disabled people), especially at road intersec- catenary-free technologies are available nowadays [8]: tions which are absolutely crucial for the operating con- • Ground-Level Power Supply (GLPS) Power continu- ditions of the global road network (GRN) in terms of ously supplied to the vehicle at ground level via direct functionality and safety. contact with a conductor or inductively (Ansaldo Although tramway accidents are very limited in number TramWave, Alstom APS etc.); if compared to the total road accidents, their consequences, • Onboard Energy Storage System (OESS) Power stored especially when involving pedestrians, are so serious that on the vehicle, using flywheels, batteries (Ni-MH, Li- cannot be neglected by transportation and highway engi- Ion etc.), supercapacitors or a combination thereof, neers. In the light of the brief considerations above, this recharged periodically via regenerative braking and paper first analyses the road accident rate and its evolution contact with a power conductor; in the last 10 years with specific regard to operating Italian • Onboard Power Generation System (OPGS) Power tramways and then outlines the main strategies introduced continuously generated on the vehicle as required via worldwide to improve the tram safety system in the urban hydrogen fuel cells, micro-turbines or diesel engines. environment. Such strategies are aimed at better warning road users of These systems have received acclaim for eliminating the specific risk conditions on the one hand, and on the other, need for overhead wires and preserving the aesthetic form they are designed to install suitable facilities on road of the dense urban centres. The catenary-free technologies platforms: are increasingly used around the world. • for better informing users of tramway system (also by 1.2 Growth Trend in the Tramway Transport means of acoustic signals); System and Accident Rate: The Italian Case • for limiting or temporarily prohibiting turning move- ments or manoeuvrings; Rail transport in urban/suburban areas (tramway system) • for properly channelling pedestrian and vehicle flows went into decline in the 1970s (Fig. 1) but it has been so as to avoid or reduce interference with trams. rediscovered and boosted since 2000 [9, 10]. In fact, the total domestic traffic in the urban tram transport has 1.1 Classification of Tramway Systems increased in the last 10 years from 1053 million passen- gers-km in 2005 to 1305 million passengers-km in 2015 Modern tramways are mass public transport systems in [11]. Also the suburban tram transport has significantly urban and suburban areas characterised by commercial grown from 50 million passengers-km in 2005 to 85 mil- speeds of 12*30 km/h and actual passenger capacity of lion passengers-km in 2015. the order of 6000 passengers/h/per direction. They can be In 2005, the total extension of the urban/suburban classified as follows [6, 7]: tramway network in operation was 457 km and 516 km in 2015. Despite the upward trend, the private mode still • Common corridor (class E) Railway vehicles are mixed prevails over the public means of transport: precisely in with road vehicles and pedestrians; 2015, the percentage transport mode distribution was [11]: • Exclusive Separated Corridor (Class D) Grooved rails 4.5% motorcycles, 83.8% private vehicles, 11.7% public are also used, but they are separated from the general transport. traffic by means of horizontal lining or obstacles In 2016 in Italy, there were in all 175,791 road accidents accessible to pedestrians; with seriously injured casualties, among which were 3283 • Exclusive Tram Corridor (Class C) The existing road is died in 30 days and 249,175 wounded [12]. used solely for the movement of the tram while the The available data indicate a relatively safe tram trans- remaining road width is pedestrianised; port system. Suffice it to say that in the same 2016, there • Exclusive Protected Corridor (Class B) The tramway is were 46 one-vehicle accidents (of which 41 involving completely separated from the circulation of road pedestrians) and 116 crashes involving other vehicles [12]. vehicles and pedestrians; It is also worth considering that thanks to the positive • Fully Exclusive Corridor (class A) Tramway vehicles transport demand trend and the consequent tramline move as in the previous case (class B) on flat bottom expansion in old town centres together with the increas- rails, at grade, or underground or elevated section. ingly efficient catenary-free systems, accident numbers are The most distinctive functional and geometric charac- certainly doomed to grow. teristics based on the type system are given in Table 1. In order to make the tramway transportation system safer, a careful investigation should be conducted into the 123 Urban Rail Transit (2018) 4(4):223–233 225 Table 1 Features and characteristic values related to tramway systems. Source: Adapted from [7] Minimum horizontal curvature radius R =20*25 m, preferred value R C 30 m R =15*18 m at shunting tracks Types of track integration A single track per direction at the opposite sides of the roadway A double track on one side of the roadway Central alignment (double track) Types of stops integration Stop with centre (Island) platform Stop with laterally staggered platforms Stop with laterally opposed platforms Distance between two successive stops 200 m*800 m Types of power supply system (catenary overhead system Central mast and opposite cantilevers integration) Lateral mast and double-track cantilevers Catenary connected to laterally opposed masts Catenary connected to building facades Mixed catenary connection (on one side to lateral masts and on the other to building facades) Vehicle length Simple: 8*18 m, Articulated: 18*30 m, Multiarticulated: 25*45 m Vehicle width 2.20*2.65