Intelligent Speed Adaptation: Preliminary Results of On-Road Study in Penang, Malaysia

IATSS Research 36 (2013) 106–114

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IATSS Research

Intelligent speed adaptation: Preliminary results of on-road study in Penang, Malaysia

S.M.R. Ghadiri a,⁎, J. Prasetijo a, A.F. Sadullah a, M. Hoseinpour a, S. Sahranavard b a School of Civil Engineering, University Sains Malaysia (USM), 14300 Nibong Tebal, Penang, Malaysia b Shahid Beheshi University, Tehran, Iran article info abstract

Article history: The first field experiment with intelligent speed adaptation (ISA) in Malaysia was held in December 2010 in Received 15 March 2012 the State of Penang. Eleven private cars were instrumented with an advisory system. The system used in the Received in revised form 1 August 2012 present study included a vocal warning message and a visual text message that is activated when the driver Accepted 6 August 2012 attempts to exceed the speed limit. When the driver decreases the speed, the warning stops; otherwise it is continuously repeated. The test drivers drove the vehicles for three months with the installed system, and the Keywords: speed was continuously logged in all vehicles. The warning was however only activated in the second month Advisory ISA system Driving behavior of the three month period. The present study aimed to evaluate the effects of an advisory ISA on driving Intelligent speed adaptation speed, traffic safety, and drivers' attitude, behavior, and acceptance of the system. To examine these effects, Safety both the survey and the logged speed data were analyzed and explored. The results show a significant reduc- Speed control tion in the mean, maximum and 85th percentile speed due to the use of the system. However, there was no long-lasting effect on the speed when the system was deactivated. In the post-trial survey, drivers declared that the system helped them well in following the speed limits and that it assisted them in driving more com- fortably. Furthermore, the warning method was more accepted compared to a supportive system, such as active accelerator pedal (AAP). After the trial, most drivers were willing to keep an ISA system. © 2012 International Association of Traffic and Safety Sciences. Production and hosting by Elsevier Ltd. All rights reserved.

1. Introduction in the risk of death. According to Nilsson [9], the number of fatal and serious-injury accidents, for example, decreases by almost 25% when Annually millions of road users are killed or injured in trafficacci- the speed decreases from 55 km/h to 50 km/h. Warner and Aberg dents [1]. Road-traffic accidents were ranked as the ninth most com- [10] declared that approximately one-fifth of all people killed would mon cause of death in 1990 and are estimated to be the third most have survived if drivers had remained within the speed limits. common cause of death by 2020 [2]. Furthermore, fatalities are Analysis of the data recorded by the Royal Malaysian Police re- projected to increase by over 80% in developing countries and by 65% vealed that the rate of speeding-related accidents in all states has including the developed countries by 2020 [3].TrafficaccidentsinMa- been increasing noticeably. Speeding was the reason for 11.4% of all laysia have been increasing at an average rate of 9.01% per annum from crashes in 2010 compared to 0.59% in 2002. Likewise, the percentage 1974 to 2010 [4,5]. Malaysia is estimated to have over 20 fatalities per of speeding-related fatal accidents per total fatal accidents increased 100,000 people in 2020 [3]. Excessive speed is considered to be the from 19.8% in 2002 to 25.4% in 2010, which is equivalent to a growth major contributory factor to road accidents, injuries and deaths. The of 28.4% [4,12]. Reduction in speeding therefore seems to be a logical strong relationship between vehicular speed and accidents has been way to improve road traffic safety. Improving road safety is a major demonstrated in several studies over the years. One of the findings indi- concern, and road safety advocates around the world dedicate exten- cated that lower speed variance is correlated with fewer accidents (see sive resources to solve speeding problem, mainly through the compli- e.g. [6–11]). Finch et al. [7] declared that reducing speed by 1 km/h can ance with speed limits. Currently, various policy efforts, including lead to a 3% decrease in accidents resulting in injury and a 4–5% decline education (e.g., driving license education and campaigns), enforcement (e.g., police surveillance and speed cameras), or different types fi ⁎ Corresponding author. Tel.: +60 147580100. of physical measures in the traf c environment such as road humps, E-mail address: [email protected] (S.M.R. Ghadiri). are being undertaken to decrease the level of speeding infringements Peer review under responsibility of International Association of Traffic and Safety Sciences. (for a more elaborate overview see [13]). Although, many of the traditional measures have appeared to be successful in the past, analysis of accident data shows that there is still much to be done. Many of the traditional speed control measures have had limited effectiveness in terms of their site coverage and/or duration. Recent

0386-1112/$ – see front matter © 2012 International Association of Traffic and Safety Sciences. Production and hosting by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.iatssr.2012.08.001 S.M.R. Ghadiri et al. / IATSS Research 36 (2013) 106–114 107 studies have shown that, for example, in terms of police enforcement [38]. However, despite the promising overall results of earlier studies and speed cameras, drivers tend to reduce speed only near the en- there are some arguments in terms of the implementation of ISA, such forcement area and for only a short period of time [14]. Likewise, as which system to use, and the area where the studies have been carried roadway features designed to reduce speeding tend to reduce speed out must also be taken into account. The majority of previous studies only in the specific small and limited area [15]. Recent and ongoing were concentrated in Europe with similar road-safety cultures and driv- developments in technology, including improvements in navigation ing styles. Hence, determining the effect of such a system in a different aids and intelligent in-car systems, provide possible opportunities in region with different cultural backgrounds and driving styles would be assisting drivers to adhere with speed limits. One system that is in- an issue of interest. The present study is considered to be the first exper- creasingly gaining attention is the intelligent speed adaptation (ISA). iment using an advisory ISA system in Malaysia. From December 2010 ISA, which is regarded to be a type of vehicle-based intelligent until February 2011, an ISA on-road study was carried out in Penang, Ma- transportation system (ITS), refers to an advanced in-vehicle elec- laysia. Eleven cars were instrumentedwithanadvisoryISA-systemwith tronic driving-aid system. It is a system wherein the vehicle detects the intent to study the effects of the system on speed‐change, trafficsafe- the speed limit on a particular stretch of road and can warn the driver ty, and drivers' attitude, behavior, and acceptance, a survey and analysis if he is exceeding the speed limit, subsequently discourages him from of driving data was conducted. The preliminary results obtained in the speeding, and/or prevents the speed limit from being exceeded [16]. present study are reported in this paper. Speed‐control studies for the There are a number of variations for ISA; it could be broadly classified ISA system has been started in the Universiti Sains Malaysia in 2007. into two main categories concerning its functions: warning or adviso- The present study, serves as a practical evaluation of the advisory ISA sys- ry, and limiting or automatic vehicle control [17]. The warning or ad- tem in the region. visory system provides alarms (auditory, visual, or haptic) when the system identifies and determines that the driver has exceeded the 2. Materials and methods speed limit. The limiting system, also known as the mandatory ISA system, prevents the driver from exceeding the speed limit by 2.1. Study design and procedure adjusting the engine speed or braking control, among others. Most ISA systems use Global Positioning System (GPS) in combination The fieldwork experiment was carried out for three months from with a digital road map that contains the information about local December 2010 to February 2011 in real traffic in the study area. All speed limit. ISA is considered to be a functional device for influencing the test drivers had an advisory ISA installed in their vehicles. They drivers' speeding behavior, thus contributing to the promotion of first drove for one month without activating the system and, their “nor- road safety. The concept of speed adaptation by in-car systems as mal” driving speed was recorded. They then drove for another two safety devices has been studied for nearly 30 years in different coun- months with the system activated for one month and again deactivated tries. In the last decade, several trials involving different types of ISA for another month, respectively. One week prior to the installation of have been conducted across Europe and Australia. ISA has also been the device in November 2010, the observation method was employed under investigation in many other countries around the world. to measure the average speed for all vehicles. Observations were carried In the Netherlands, in a series of Dutch simulator experiments, vi- out by an observer who accompanied the driver. The average speed of sual and auditory messages have been employed when a breach of the vehicle was determined by measuring the travel time. This was speed limits is detected. The message, which says “you are driving done to determine if there is any difference between the participants' too fast; the current speed limit is XX” was delivered by a female usual driving speed with and without the device (side effect of the pres- voice and/or alternatively, the text was projected on the simulator ence of the device). screen. The results of these studies showed the positive effect of this The data was logged during the three-month study period. This was type of ISA in terms of its usefulness, although it has a low satisfaction started as soon as the device was switched on. Weather and road condi- rating among young drivers [18–21]. A study by Aalborg University in tions were also monitored during the on-road study, and data on days Denmark also showed the positive effects of the advisory system on with extreme conditions were excluded from the analysis. The analysis speed limit compliance [22]. The researchers tested a speed limit was carried out for three specific periods: the month without feedback warning system in which a flashing red LED display and a friendly fe- (warning off), the month with feedback (warning on), and the month male voice were given when the drivers exceeded the speed limit. when the feedback function was again deactivated (warning off again). The overall reduction in the average speed was 5–6 km/h. The results These periods are referred to as “before”, “during”,and“after” (for of a large-scale Swedish field trial with the “BEEP” system in Borlänge more illustration, see Fig. 1). The subjective data was collected twice dur- showed that the test drivers behaved more positively in accordance ing the study through a questionnaire: once at the beginning and again with the traffic rules due to the system. One of the main results of atthesecondmonthwhenthedriversareusingthesystem.Tofurther such a trial was an average speed reduction of 0.6–3.4 km/h [23,24]. minimize potential technical and other unpredictable problems during The results of field trials on ISA in the UK were also promising, show- the study with the system, a preliminary test study with one participant ing a reduction in the 85th percentile speed and in the frequency of going was organized for almost two weeks between September 27 and Octo- over the speed limit. These in turn resulted in a decrease in injury and ber 12, 2010 before the commencement of the main on-road study [39]. crash risks [25,26]. In Australia, an on-road evaluation of ISA was carried Prior to the main on-road study, all drivers were interviewed sepa- out from 2002 to 2004 under the TAC Safecar project in the Melbourne rately. Participants were first informed about in-vehicle information area. The results showed that the 85th percentile speed and speeding Before During After with more than 5 km/h were reduced by up to 2.7 km/h and 65%, respectively [27]. Experiments in simulator and trial studies with haptic systems (e.g., accelerator pedal and the dead throttle) also showed the positive Installation Activation Deactivation Dismantling effects of this type of ISA on drivers' speeding behavior [28–35]. Time line A comparison study of the different types of ISA revealed that even 1 month 1 month 1 month though the limiting system was the most effective and useful in reducing speed, it is not popular among drivers. Instead, the informative and Before After warning system had the highest acceptance [36,37]. Previous trials on questionnaires & questionnaire & ISA throughout the world have demonstrated not only its potential for Interview Interview reducing the risk and severity of accidents, but also its other societal benefits such as improving drivers' interactions with other road users Fig. 1. Schematic view of study's procedure. 108 S.M.R. Ghadiri et al. / IATSS Research 36 (2013) 106–114 systems in general terms and more specifically about the purpose of the (near the two toll plazas), and 110 km/h at the middle. The total length study. An “operation manual” containing a brief overview of ISA sys- of segment I (speed limit of 50 km/h) was 2 km, segment II (speed limit tems, the procedure of the study, and the log book was distributed to of 60 km/h) was 1.2 km, and segment III (speed limit of 110 km/h) them. All drivers then completed a general questionnaire asking them was about 15.5 km. This corridor is part of the longest expressway in to provide their personal information, driving experience, and ideas Malaysia (North–SouthExpressway[NSE]),withatotallengthof about further speed, and speed-restriction systems. All participants 772 km running from Bukit Kayu Hitam in Kedah near the Malaysian– signed the agreement letter of participation and filledupthe“before” Thai border to Johor Bahru at the southern portion of Peninsular Malaysia. questionnaire, which included specific questions about the on-road study and soliciting their views with respect to ISA systems. The ques- 2.3. The test drivers tionnaire further covered the emotional state (stress, driving enjoyment, etc.), system features, and drivers' willingness to maintain and pay for Eleven participants, both male and female, were selected from a the systems. As an honorarium and compensation for the inconvenience group of volunteers who replied to the “recruitment letter”. The letter caused, the drivers received Malaysian Ringgit (MYR) 360 per month. included information about the project and a question asking whether Thereafter, the system was installed in all the participants' cars. they want to participate or not. The selection criteria was that the par- Drivers were instructed to drive as they would normally do in their ticipants must be between 25 and 50 years old, should possess a driving own car. The system was activated by the drivers when the cars entered license for more than five years, should have driving practice of at least the test area, after which it could not be turned off. At the end of the sec- 5000 km per annum and own a car not older than a 1995 model. In ad- ond month, participants were again interviewed and were requested to dition they should have no prior experience with the test system complete the “after” questionnaire. Some of the questions from the “be- [17,40,10,37]. Moreover, drivers who use the test area more frequently fore” questionnaire were repeated in the “after” questionnaire. The were given preference for recruitment. The participants, six male and “after” and “before” questionnaires contained between 7 and 22 ques- five female drivers aged between 25 and 45 and with an average age tions each, most of which were to be answered on a five-grade Likert of 33, have held driving licenses for between 5 and 14 years (see scale. Nominal scale was also used. All the drivers fully completed the Table 1). The drivers drove a range of different vehicles; Naza (2010), questionnaires. Myvi (2009), Toyota Vios (2008), Toyota Harrier (2007), Perodua Kelisa (2005), Proton Savy (2005), Proton Wira (2003), Kembara (1999), Renault (1998), Proton Iswara (1997), and Honda Civic (1996). 2.2. The test sites

Aspeciﬁc route of over 18 km, which takes approximately 15 min to 2.4. The system drive, was selected. The test site was a corridor in the state of Penang, in the north-west part of Malaysia, located between two toll plazas (see The system was a GPS receiver, which was manufactured by Fig. 2). The test road environment has varying speed limits of 50, 60 Garmin, and made up of two components — a navigation unit with

Fig. 2. The study area. S.M.R. Ghadiri et al. / IATSS Research 36 (2013) 106–114 109

Table 1 involving accidents and injuries change when the average speed Demographic details of participants. changes in a road network, with every parameter remaining constant. Gender Male Female However, the equations shown below have been selected from the power model. Mean age (S.D.) 34.83 (9.72) 29.2(3.03) Marital status Single 2 3 . 4 Married 4 2 Number of fatal accidents ¼ Y ¼ V1 Y Divorced 0 0 1 0 V1 Education Under diploma and diploma 3 1 . 3 ¼ V1 University 3 4 Number of serious injury accidents Y1 Y0 Driving experiences 5 to 10 years 2 4 V0 More than 10 years 4 1 where, speed is V, accidents is Y and subscript by 0 the values observed before a change in mean speed and by 1 the values observed a digital map containing all the current speed limits within the test after a change in mean speed. The system's effect on drivers' attitude area and a data recorder. The device continuously identifies the posi- was considered by three different questions, both before the start of tion of the vehicle, calculates the speed, and compares this with a dig- the on-road study and when the participants are using the system. ital map to determine the speed limit at such position. The recorded The first question was about the effectiveness of the system on im- data including speed limit, speed, position, and time were logged on proving speeding behavior: “Do you think that it would be an effec- the device's internal memory whenever the system is switched on. tive system to change and improve drivers' speeding behavior?” In The interface to the driver consisted of a display positioned in front the second question, drivers' idea about the effectiveness of the sys- of the driver showing the current speed limit, a digital map, an audi- tem on reducing stress was asked: “Do you think that ISA would be tory warning (vocal message), and a text projected on the screen an appropriate and effective system to reduce your stress during driv- when the speed limit is exceeded. The warning was repeated every ing?” In the third question, the system's effectiveness on the reduc- three seconds as long as the vehicles' speed remains higher than the tion of injury and fatal accidents was asked: “Do you think that if all recommended speed limit. drivers use this technology it will be effective and help to reduce se- The content of the message –“danger, danger, please reduce your rious injuries and fatalities in your community?” The questions were speed”–was given by a female voice and alternatively, the text answered on a five-grade Likert scale where one means “not effective”, projected on the device's screen reads “speed limit is XX”, giving two means “somewhat effective”, three means “effective”,fourmeans warning to the driver. Mapsource and POI Loader were used to create “very effective”,andfive means “extremely effective”. and assign the warning. Moreover, whenever the speed limit is exceeded, the color of the current speed display on the screen 3. Results changes from black (complying with the limit) to red (warning that the limit is passed). The drivers repeatedly receive these warnings 3.1. The system's effects on driving speed until the speed returns to below the recommended speed limit. It was still possible to accelerate. If the driver reduces speed, the warn- The Mann–Whitney U test revealed that there was no statistical dif- ing will stop; otherwise, the warning will be continuously repeated. ference between the mean speed from the data recorded by the devices from the “before” period and the mean speed that has been calculated 2.5. Analysis method by the observers before the device installation (p=0.068>0.05). This confirms that even if the mean speed slightly decreased after the device The data generated was stored in a database, in which every entry installation (about 2.6% reductions), the existence of the device did not in the vehicles' log files was attributed to a trip. The data was tested statistically affect drivers' usual driving speed. The analysis of speed for statistical difference through an analysis of variance (ANOVA). A data was made for all three segments: 50, 60, and 110 km/h. For all significance level of p≤0.05 was used to analyze the possible differ- segments, the warning system brought about a statistically sig- ences in the mean speed among the three conditions (“before”, “dur- nificant reduction in the mean speed (segment I: F(2,731)=18.930, ing”, and “after”). Post hoc multiple comparisons were carried out p=0.0001b0.05; segment II: F(2, 676)=8.210, p=0.0001b0.05; seg- using the Scheffe test and the Tamhane's T2. Since differences ment III: F(2,599)=18.768, p=0.0001b0.05). Tables 2–4 show that among the ISA conditions are expected, the use of such tests, which the mean speed was mainly reduced by up to 4.27 km/h for segment are not too conservative, is justified. Moreover, to assess the system's III, where the speed was the highest. The reduction for segments I and effect on drivers' attitude, the Wilcoxon signed-rank test was also II was 3.6 and 3.38 km/h, respectively. The results also show the reduc- employed. tion in the 85th percentile speed and the speed variance due to the sys- To study the behavioral effects for the Penang ISA study, the fol- tem. The 85th percentile speed was almost identically reduced by up to lowing parameters were examined: average speed, standard devia- 4.5 km/h on segments I and II, whereas a large decline of up to 5.5 km/h tion, and 85th percentile speed. Furthermore, since there is higher was recorded on segment III. Furthermore, the figures show that even if risk of being involved in an accident when the driving speed differs there was again an increase in speed after the drivers stopped using the from the mean speed [7], the variation of speed was also studied. Hence, a reduction in speed deviation indicates that ISA can reduce the number of accidents. The non-parametric Mann–Whitney U test Table 2 Speed data for all cars for different periods of study on the segment I (50 km/h). was employed to assess the statistical significance of the differences in the mean speed between the observed data by the observers and Period N Mean speed Standard 95% confidence 85th the data recorded by the device. t-test was used to assess the statisti- (km/h) deviation interval for mean percentile (km/h) (km/h) cal difference between the mean speeds or the mean of the maximum Lower Upper speeds based on the participants' characteristics on the p≤0.05 level. bound bound Chi-square test (X2) was used to test for significance associations be- Before 203 62.78 7.5 61.74 63.81 73 tween drivers' responses to the “before” and “after” questionnaire. During 333 59.18 7.41 58.38 59.98 68.5 The system's effect on safety was modeled with the power model After 198 62.05 6.42 61.15 62.95 73 introduced by Nilsson [41,9]. The model describes how situations N=The total number of car passages. 110 S.M.R. Ghadiri et al. / IATSS Research 36 (2013) 106–114

Table 3 Segment I (50 km/h) Speed data for all cars for different periods of study on the segment II (60 km/h). Segment II (60 km/h) Period N Mean speed Standard 95% conﬁdence 85th (km/h) deviation interval for mean percentile Segment III (110 km/h) (km/h) (km/h) Lower Upper 110 bound bound 105 Before 201 54.33 11.45 53.04 55.63 82.5 During 337 50.95 9.34 49.71 52.18 78 100 After 197 53.6 9.99 52.16 55.02 82 95 90

Table 4 85

Speed data for all cars for different periods of study on the segment III (110 km/h). km/h 80 Period N Mean speed Standard 95% conﬁdence 85th 75 (km/h) deviation interval for mean percentile (km/h) (km/h) Lower Upper 70 bound bound 65 Before 199 94.86 10.34 93.41 96.31 108 60 During 346 90.59 8.85 89.65 91.52 102.5 Before During After After 202 94.69 8.51 93.51 95.87 105.5

Fig. 4. The 85th percentile speeds of all test cars when driving with and without the system on the different segments during the three periods of the on-road study. system, the speed level did not reach the same level as it was before (see also Figs. 3 and 4). shows this trend graphically for all three segments, with the fast seg- The major effect of the ISA system was observed at the highest ment (segment III) showing the trend clearer. speed, and the changes in the 85th percentile speed is a very good in- It was hypothesized that the system will bring a reduction in dicator of this (see Fig. 4). Analysis of the maximum speed of all the speed variance, especially at the highest speed as shown in earlier test cars revealed that ISA system caused a statistically significant studies on ISA. The present study showed a clear decrease in speed reduction in the average of the maximum speeds for the three seg- variance (see Tables 2–7), and this effect is apparently largely due ments (Segment I: F(2,563)=22.370, p=0.0001b0.05; Segment II, to the reduction in the highest speed (see also Fig. 5). F(2,732)=19.757, p=0.0001b0.05; Segment III: F(2, 586)=35.466, As shown in Fig. 6, the highest speed decreased when the system p=0.0001b0.05; see also Table 5–7). was working, and increased again when the system was deactivated. A large reduction in the average of the maximum speeds of up to The speed changes were further analyzed using the data from the 7 km/h was observed for segments I and III, with speed variance drivers' vehicles and from the questionnaire; it was possible to also recording a decrease due to the ISA system (see also Figs. 5 and 7). study the change in the mean and the maximum speed in more de- In the presence of significancefortheomnibusANOVAtest,theScheffe tails. The analysis showed that the mean speed concerning different and the Tamhane's T2 multiple comparison tests were used to perform characteristics decreased after the activation of the warning system, pair-wise comparisons. However, such analysis was separately and such reductions were statistically significant according to the performed for the three segments. The analysis revealed that the mean t-test, p≤0.05 (see Table 8). and the mean of the maximum speeds statistically decreased significant- As expected, male drivers drove their vehicles faster than the fe- ly when the drivers received warning during the second period of the male drivers. Married drivers were inclined to drive slower at the study. Nevertheless, there was no statistically significant difference be- high-speed environment (segment III) than the singles, and the dif- tween the drivers' mean speed in the first and third periods. ference between the mean speeds of single and married drivers in Previous studies on advisory systems (e.g., beep system or AAP) this segment was statistically significant. Table 8 demonstrates that showed that it has a large initial effect and that the effect somewhat more experienced drivers and those who drive new-model cars diminishes over time (see [35,38,37]). The analysis of speed data in were inclined to drive significantly faster than their counterparts. the present study confirms such findings. The reduction in the mean speed in the initial weeks was more than that in the last weeks of 3.2. Drivers' opinion, attitude, and behavior the second month when the drivers received feedback. However, when the feedback was stopped, the drivers' average driving speed Almost all participants indicated that ISA helped them experience a gradually returned to somewhat the same level as before. Fig. 6 feeling of increased safety when driving with the system. They believed

100

80 Before

60 During 40

20 Mean speeds km/h After

0 Segment I (50 km/h) Segment II (60 km/h) Segment III (110 km/h)

Fig. 3. Mean speeds of all test cars when driving with and without the system on the different segments during the three periods of the on-road study. S.M.R. Ghadiri et al. / IATSS Research 36 (2013) 106–114 111

Table 5 50 km/h 60 km/h 110 km/h Entire Speed data for all cars for different periods of study on the segment I (50 km/h). 120 Period N Average of maximum Standard 95% conﬁdence speeds (km/h) deviation interval for mean 100 (km/h) Lower Upper 80 bound bound

Before 203 82.65 15.4 80.52 84.78 60 During 333 75.13 12.76 73.75 76.5 After 198 79.36 9.84 77.98 80.74 40

N=The total number of car passages. Mean Speed km/h 20

0 Table 6 1 and 2 3 and 4 5 and 6 7 and 8 9 and 10 11 and 12 Speed data for all cars for different periods of study on the segment II (60 km/h). Weeks Period N Average of maximum Standard 95% conﬁdence speeds (km/h) deviation interval for mean Fig. 6. Change in mean speeds per two weeks for the segments and the Entire corridor. (km/h) Lower Upper bound bound using the system. This conﬁrms the high acceptance level of the concept Before 201 87.67 11.54 86.06 89.27 of the system among the majority of the participants. During 337 81.88 10.93 80.71 83.06 “ ” After 197 86.20 10.97 84.66 87.74 Data from the after questionnaire was tested against accident involvement and speeding offenses (self-reported from the “before” questionnaire); there was no difference between drivers who report-

Table 7 edly had had an accident or who had committed a speeding offense Speed data for all cars for different periods of study on the segment III (110 km/h). and those who had not (bchi>2(9)=14.226, p=0.115>0.05). There was no significant difference in the results of a comparison be- Period N Average of maximum Standard 95% confidence speeds (km/h) deviation interval for mean tween drivers who agreed that there was a strong correlation be- (km/h) tween speed and risk and those who did not. This was probably Lower Upper because most of the drivers agreed that a strong correlation exists. bound bound In the “before” questionnaire, nine of the drivers indicated that they Before 199 113.27 11.12 111.71 114.82 believe that more than 40% of all fatal crashes and serious accidents During 346 105.95 9.11 104.98 106.91 After 202 109.81 9.20 108.54 111.09 could have involved speeding, and two said that the level was at 30–40%. This shows that drivers perceive that speeding was a major contributor to accident involvement. Furthermore, the majority of that if all cars were equipped with a warning system, it could help de- them (nine drivers) indicated that the recommended speed should crease the level of speeding. Furthermore, the non-parametric Wilcoxon be followed exactly, and all declared that it is important to take action signed-rank test revealed that the participants' belief in the system's ef- against speeding. To test their idea about ISA before and after using fectiveness significantly improved (Z=−2.229, p=0.026b0.05) after the system, two different questions were asked concerning the eagerness of the participants to buy the system and their opinion about the policy of imposing ISA in all cars in their community. Table 9 indicates Segment I (50 km/h) that the policy of imposing ISA in the community was relatively well Segment II (60 km/h) supported by the majority of participants and that their eagerness to buy the system is also considerable. These findings show that ISA has Segment III (110 km/h) a positive influence on drivers' attitude. 120 To determine how the participants think about the different types of advisory ISA, they were also asked to identify the type of advisory 115 ISA they prefer to use: warning system (e.g., beep or vocal warning) or physical speeding prevention such as accelerator pedal, which 110

105 Before During After 100 100 90 95

km/h 80 90 70 60 85 50 40

80 Percent % 30 75 20 10 70 0 Before During After 70 80 90 100 110 120 130 140 150 Speed (km/h) Fig. 5. Average of maximum speeds of all test cars when driving with and without the system on the different segments during the three periods of the on-road study. Fig. 7. The cumulative speed distribution for max speeds in the segment III from all cars. 112 S.M.R. Ghadiri et al. / IATSS Research 36 (2013) 106–114

Table 8 The mean speed (km/h) for drivers with regard to their experience of ISA and other characteristics.

Segments Periods Gender Age (years old) Marital status Driving experience Car years

Male Female 35> 35b Single Married Under 10 years Over 10 years 2005> 2005b

I Before 61.64b 64.1a,b 63.08b 61.91 63.32b 62.33b 63.25b 62.15b 62.59b 62.94b During 59.03 59.4 58.98 59.81 59.2 59.17 58.84 59.74 58.49 60 II Before 61.47a,b 53.35b 53.55b 56.58 52.08 56.24a,b 53.44b 55.55 51.92b 56.5a,b During 51.3 50.45 49.88 54.02a 50.49 51.4 49.56 53.23a 48.75 53.57a III Before 95.47b 94.15b 93.13b 99.64a,b 96.54a,b 93.5b 93.92b 96.07b 93.59b 95.93b During 90.8 90.3 89.41 94.1a 91.92a 89.36 90.07 91.54 89.48 91.85a Entire Corridor Before 80.37b 79.84b 79.18b 82.72a 80.84b 79.55b 79.71b 80.66 79.17b 80.93 During 78.12 76.84 76.53 80.73a 77.81 77.38 76.74 78.9a 77.19 80.25a

a Signiﬁcantly higher mean speed than their horizontal counterpart according to t-test, pb0.05. b Signiﬁcantly higher mean speed than their vertical counterpart according to t-test, pb0.05.

has been tested in Sweden [35,42]. In both the preliminary and post present study confirm this since the system had lower effect in seg- questionnaires, the majority of the participants were more positive ments I and II which are near the toll plaza compared with in segment about having the warning system (e.g., vocal or beep system) in III (middle of the corridor) (see Tables 2–4). With reference to knowl- their own cars compared with having a more restrictive system edge about the importance of speed variance and maximum speed for (AAP) — 9 and 8 drivers respectively. traffic safety, it is very important to know that even a small difference in the mean speed can have a great effect on traffic safety (see 3.3. Safety estimation [44,7,45]). However, it was also found that the variance in speed decreased, largely by the reduction of the highest speed. The effect of the system on safety was estimated using the power The system's effect on serious-injury accidents, based on reduc- model, which used the aggregated speed data for the different seg- tions in the mean speed, was estimated to be 13–18% reduction. In ments displayed in Fig. 1 as the input. The results of the estimation the report outlining the results of the large-scale trial in Sweden for the reduction in injury and fatal accidents are presented in [42], it was concluded that the reduction in the number of road inju- Table 10. ries, if everyone had ISA (in that case an AAP), would be at least 20% The real effect of the system on safety was obtained in segment III, and as much as 25% (an average of 22.5%). Unlike the Swedish estima- which represented the chosen driving speed of the drivers. In this tion that used a more restricted system, i.e., AAP, which physically segment, drivers had had time to complete their acceleration from prevented the drivers from speeding, the present study used a vocal segment I and had not yet started to brake for the upcoming segment. warning system, hence the reduction of 13–18% on serious-injury accidents is considered satisfactory. 4. Discussion and conclusions The present study also indicates that the reduction in speed in the last period has no long-lasting effect and is expected to last for a short Today, one of the main concerns for road authorities around the period. In a nutshell, as shown by previous studies on ISA, the system world is increasing the adherence to speed limits. Albeit the many ef- has no long-lasting effect on speed when it is removed. It is expected forts done to improve the situation, there is still much to do. ISA is an that the effect will gradually disappear and drivers will resume with in-vehicle system that automatically determines the speed limit of their initial habit (for an example, see [37]). For the advisory system the road and warns the driver when the speed limit is exceeded (e.g., vocal warning system) to achieve a more lasting effect, it should and/or actively prevents him from committing speeding offenses. To not be removed from the vehicle and must work as a permanent gad- consider the effect of ISA on drivers' speeding behavior, various stud- get. However, the present study suggests that the system is more suit- ies have been carried out worldwide, especially in European coun- ed as a permanent assistive device than as a temporary training tries. These studies differed in the way they present the change in device. drivers' speed behavior. The value that is most typically quoted was Apart from the improved speed behavior of the drivers, the system the change in the mean and the maximum speed, 85th percentile was also shown to have an effect on other driving behavior. According speed, and speed distribution. The present study has shown that the to the drivers' self-report, their behavior in terms of interacting with overall effect of the vocal warning system on speed and safety is in other road users even outside the test area improved after using the line with the results of previous studies (see Table 11). system. The drivers stated that their degree of correct yielding behav- The analysis on the logged speed data revealed that drivers' speed ior at junctions improved, possibly due to an increased awareness of when driving with the system was significantly reduced, especially the surrounding traffic as a result of the reduced speed with the use on segment III where they could choose their speed more freely with- of the system. These finding are in line with those of previous studies out being encumbered by other speed-reducing measures. Previous studies on ISA stated that the infrastructure and surrounding traffic Table 10 have greater impact on speed than the drivers' preferred speed and The expected decrease in injury and fatal accidents after the introduction of the AISAS that the ISA system has little or no effect [43,35]. The findings of the according to the Power model. Segment/speed Mean speed E1 E2 Table 9 limit (km/h) (km/h) Drivers opinion about imposing ISA and their eagerness to buy the system. 3 4 V1 V2 (1−(V2/V1) )∗100 (1−(V2/V1) )∗100 Question Before After I/50 62.78 59.18 16% 21% II/60 54.33 50.95 18% 23% Yes No Yes No III/110 94.86 90.59 13% 17% Are you willing to buy ISA for your car? 8 3 8 3 V1=Without system , V2=With system. Do you support the policy of imposing ISA in all 8392 E1=Expected decrease in the number of serious-injury accidents %. cars in your community? E2=Expected decrease in the number of fatal accidents %. S.M.R. Ghadiri et al. / IATSS Research 36 (2013) 106–114 113

Table 11 The summary results of recent advisory ISA trial study in some countries.

Location Year of study Light vehicles Heavy vehicles Speed zones (km/h) Change in mean speed (km/h) Change in 85th% speed Reference

Groningen, Netherland 1999 24 None 50–120 −4 – [18] Borlänge, Sweden 2001 400 None 30–110 −0.6 to −3.4 – [24] France, Paris 2001 22 None 30–130 −0.8 – [48] Finland 2001 24 None 40–80 −2.8 – [36] Aalborg, Denmark 2001 24 None 50 −5to−6 – [22] Debrecen, Hungary 2003 20 None 50 −0.7 −1.8 [37] Mataro, Spain 2003 20 None 30–120 −1.9 to −2.8 −0.4 to −5 [37] Ottawa, Canada 2006 10 None 40–100 ––[49] Penang, Malaysia 2010 11 None 50–60–110 −3.3 to −4.3 −4.5 to −5.5 –

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