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Purpose – This study aims to investigate the safety effects of work zone advisory systems. The traditional system includes a dynamic message sign (DMS), whereas the advanced system includes an in-vehicle work zone warning application under the connected vehicle (CV) environment. Design/methodology/approach – A comparative analysis was conducted based on the microsimulation experiments. Findings – The results indicate that the CV-based warning system outperforms the DMS. From this study, the optimal distances of placing a DMS varies according to different trafﬁc conditions. Nevertheless, negative inﬂuence of excessive distance DMS placed from the work zone would be more obvious when there is heavier trafﬁc volume. Thus, it is recommended that the optimal distance DMS placed from the work zone should be shortened if there is a trafﬁc congestion. It was also revealed that higher market penetration rate of CVs will lead to safer network under good trafﬁc conditions. Research limitations/implications – Because this study used only microsimulation, the results do not reﬂect the real-world drivers’ reactions to DMS and CV warning messages. A series of driving simulator experiments need to be conducted to capture the real driving behaviors so as to investigate the unresolved-related issues. Human machine interface needs be used to simulate the process of in-vehicle warning information delivery. The validation of the simulation model was not conducted because of the data limitation. Practical implications – It suggests for the optimal DMS placement for improving the overall efﬁciency and safety under the CV environment. Originality/value – A trafﬁc network evaluation method considering both efﬁciency and safety is proposed by applying trafﬁc simulation. Keywords Connected vehicles, Driver behaviors and assistance, Intelligent vehicles, Vehicle dynamics and control, Vehicle-to-infrastructure communication (V2I), Work zone, Dynamic message sign (DMS), In-vehicle warning, Trafﬁc simulation Paper type Research paper Compared to the fatalities in 2010, the number of work zone Introduction fatalities has increased by 38%. In particular, the numbers of Highway maintenances are essential to keep operational truck- and pedestrian-involved work zone fatalities have efﬁciency and safety. During the maintenance, the highway increased by 99% and 69%, respectively, from 2010 to 2017. capacity signiﬁcantly decreases and the crash risk increases. The number of work zone workers who were killed in trafﬁc Regular and irregular highway maintenances are essential to keep operational efﬁciency and safety. In developing countries, there are many highway constructions because of the rapid © Suyi Mao, Guiming Xiao, Jaeyoung Lee, Ling Wang, Zijin Wang and increases in travel and freight demands. Nevertheless, during Helai Huang. Published in Journal of Intelligent and Connected Vehicles. Published by Emerald Publishing Limited. This article is published under the maintenance and construction phases, the highway capacity the Creative Commons Attribution (CC BY 4.0) licence. Anyone may signiﬁcantly decreases, whereas the crash risk increases. In the reproduce, distribute, translate and create derivative works of this article USA, 809 people were killed at work zones in 2017 (Figure 1). (for both commercial and non-commercial purposes), subject to full attribution to the original publication and authors. The full terms of this licence maybe seen at http://creativecommons.org/licences/by/4.0/ The current issue and full text archive of this journal is available on Emerald legalcode Insight at: https://www.emerald.com/insight/2399-9802.htm This study was funded by National Key R&D Program of China (2020YFB1600400), Innovation-Driven Project of Central South University (2020CX013) and Shanghai Sailing Program (19YF1451300). Journal of Intelligent and Connected Vehicles Received 16 July 2020 4/1 (2021) 16–27 Revised 13 December 2020 Emerald Publishing Limited [ISSN 2399-9802] [DOI 10.1108/JICV-07-2020-0006] Accepted 5 February 2021 16 Safety effects of work zone advisory systems Journal of Intelligent and Connected Vehicles Suyi Mao et al. Volume 4 · Number 1 · 2021 · 16–27 experimental design section explains the main idea of the research Figure 1 Trafﬁc fatalities at work zones in the USA (2010–2017) and the result section summarizes the ﬁndings. Subsequently, the discussion section explains and interprets the ﬁndings. Finally, conclusions are drawn in the conclusion section. Methodology In this study, microsimulation was applied to achieve the abovementioned objectives. Microsimulation has been popularly used for evaluating effectiveness of safety of ITS and CV applications at network level (Wang et al.,2017; Rahman et al., 2018). Different case-controlled experiments were 2010 2011 2012 2013 2014 2015 2016 2017 designed by using microsimulation software VISSIM. Total Fatalities Truck-involved Fatalities An 8 km, three-lane highway was built in VISSIM. The Pedestrian-involved Fatalities Fatalities of Work Zone Workers speed limit is 120 km/h, and the lane width is 3.75 m. The length of work zone is 500 m. The distances between DMS crashes were 106 and 132, respectively, in 2010 and 2017 and the work zone are different by scenarios. Thus, eight (National Work Zone Safety Information Clearinghouse, different distances (i.e. 400 m, 600 m, 1,000 m, 1,400 m, 2019). The statistics indicate that trafﬁc safety at work zones is 1,800 m, 2,200 m, 2,600 m and 3,000 m) were considered. getting worse, and safety researchers should provide effective Two data collection points were installed at 500 m from the solutions to enhance safety at work zones. upstream of DMS and the downstream of the work zone, There have been many practices and research studies and itisworth mentioning that the length of the data suggesting ways to improve trafﬁc safety at work zones. One of collection segment is different in different scenarios the most common countermeasures is to warn drivers of the according to the research objectives. Average travel time, presence of a work zone. A DMS, which has been widely used average speed, average queue time and average delay time for trafﬁc control at work zones, was proven to effectively of all vehicles were considered as the evaluation efﬁciency inﬂuence driver behavior (Dudek, 2004; Strawderman et al., indicators and the number of time to collision (TTC) 2013). However, to ensure DMS can work successfully, drivers values less than 1.5 s was considered as the safety must notice the messages of DMS and obey the control advice evaluation indicator. (Schofer et al., 1993; Hassan et al.,2012; Jones and Thompson, The formula of TT is speciﬁed as follows: mean 2003). With the development of advanced information technologies, internet of vehicles is becoming a reality. In the N connected vehicle (CV) environment, work zone advisory TT i¼1 systems are more advanced than traditional ones by using TT ¼ (1) mean roadside devices to delivery trafﬁc information. Using these technologies, accurate information can be extracted and where TT is the average travel time of the data collection mean provided to drivers to alert them to present danger or assist in segment; i is the number of vehicle; TT is the travel time of a vehicle control to help drivers make optimal decisions at work vehicle numbered i; and N is the total number of vehicles. zones (Olia et al.,2013; Genders and Razavi, 2016; Abdulsattar The formula of V is speciﬁed as follows: mean et al.,2018). To improve the safety in the work zone, more accurate and detailed trafﬁc information should be sent to drivers through the DMSs or through the CV communication technologies (Teizer et al.,2010; Blackman et al.,2014). i¼1 V ¼ (2) mean Nevertheless, the previous studies have only focused on existing intelligent transportation system (ITS) applications or solely where V is the average speed of the data collection segment; mean CV technology applications, separately. Until the market i is the number of vehicle; V is the average speed of a vehicle penetration rate becomes sufﬁciently high, essential safety and numbered i; and N is the total number of vehicles. trafﬁc information through the existing ITS technologies The calculation formula of QT is speciﬁed as follows: mean should be provided for manually driven vehicles. Therefore, it is necessary to study how to maximize the efﬁciency and safety of highway work zone when CVs and manually driven vehicles QT are mixed in the road network. i¼1 QT ¼ (3) mean The main objective of this study is to investigate the coordinated optimization strategies for existing ITSs and upcoming CV where QT is the average queue time of the data collection technologies. In this paper, microsimulation software VISSIM is mean used to design different experimental scenarios. Different market segment; i is the number of vehicle; QT is the average queue penetration rates, different distance between DMS and work zone, time of a vehicle numbered i;and N is the total number of different trafﬁc volumes and different drivers’ compliance have vehicles. been considered. The rest of the paper is organized as follows. The The calculation formula of DT is speciﬁed as follows: mean 17 Safety effects of work zone advisory systems Journal of Intelligent and Connected Vehicles Suyi Mao et al. Volume 4 · Number 1 · 2021 · 16–27 simulator experiments cannot realistically reﬂect the inﬂuence DT of surrounding trafﬁc environment on drivers’ behaviors i¼1 DT ¼ (4) (Carsten and Jamson, 2011; Koutsopoulos et al., 1995; Olson mean et al.,2009). In this paper, a new approach based on VISSIM and genetic where DT is the average delay time of the data collection mean algorithm (GA) was proposed to simulate the drivers’ behaviors segment; i is the number of vehicle; DT is the average delay when they are passing through the work zone. According to time of a vehicle numbered i;and N is the total number of trafﬁc equalization principle, in the beginning, every driver in vehicles. the merge lane (the lane with work zone) tries to shorten his/her The calculation formula of TTC is speciﬁed as follows: improved travel time by merging into the through lane at different LF positions in the upstream. This process will carry on until all the TTC ¼ (5) improved v v drivers have the same travel time. Hence, a reasonable F L assumption was proposed, which is vehicles in the merge lane where d is the distance between the leading and following LF in the upstream of work zone merge at different positions, vehicle; v is velocity of the following vehicle; and v is velocity F L where for every vehicle, their travel times are approximately the of the leading vehicle. TTC is computed for a leading improved same. Because in VISSIM we cannot set the merging point vehicle and following vehicle, with the potential incident being consistently, we divided the interval between DMS and work a rear-end collision. The value of TTC at less than a improved zone into several subintervals of 200 m to represent different threshold value of 1.5 s is deﬁned as N , which was TTC1.5 merging positions. By setting multiple connectors and partial considered indicative of two vehicles exhibiting a high paths, different subintervals correspond to different initial probability of colliding (Van der Horst and Hogema, 1993). merging positions. If the vehicle passes through the partial Because microsimulation software lacks physical collision route decision point, it then starts to look for the opportunity to modeling, researchers usually use less-than-ideal methods to change lanes. If there is no opportunity temporarily, it will evaluate safety. Hence, the surrogate safety measurement continue to move forward until ﬁnds the right lane change TTC was chosen to identify potential of one of the rear- improved opportunity. Each subinterval corresponds to a lane change end collisions to approximate network safety. Experiments ratio, which stands for the number of drivers choosing to were designed, respectively, to represent different simulation change lane here. scenarios of traditional and advanced approaches (Figure 2). Therefore, this implies that under optimized lane-changing According to previous studies, it is difﬁcult to simulate ratios setting, travel time of every subinterval should be drivers’ response when they observe DMS. Drivers’ approximately the same. However, lane-changing ratios of each compliance rate in different DMS distance scenarios is subinterval are not easy to calculate. This new approach was used inconsistent. Many researchers have put efforts in studying this to obtain the approximate global optimal solution. GA was used topic (Ardeshiri and Jeihani, 2014; Brewer et al., 2006). Some to generate the initial population and complete the process of researchers conducted a survey questionnaire to investigate selection and variation. Initial population size is 10. Selection drivers’ compliance rate in different driving scenarios (Debnath process uses the roulette rule. Mutation probability is 0.05. The et al., 2015; Weng and Meng, 2012; Mohammadi et al.,2011). number of iterations was 50 generations. MATLAB codes are However, some literatures found that drivers’ compliance rate used to call VISSIM’s COM component function. Travel time abstracted from the results of the questionnaire survey results data of every vehicle in the data collection segment is collected was higher than real drivers’ compliance rate in most cases, and variance is calculated, which is the ﬁtness index of which shows that survey-based compliance rates are not very population. Three different trafﬁc volume scenarios are convincing enough (Lajunen and Summala, 2003; Wåhlberg simulated (i.e. 3,000 vehicles per hour [vph], 5,000 vph and et al.,2011). To better simulate real driving scenarios, some 10,000 vph), which represent different trafﬁc volume conditions. researchers used driving simulators to study the compliance Because a single simulation might suffer instability, each rate (Rahman et al.,2017; Whitmire et al.,2011; Bella, 2005; experiment was simulated by setting different random seeds for Shakouri et al.,2014). Nevertheless, other studies pointed out that there are still errors when using driving simulators. ensuring the accuracy and stability of the simulation results. The Because the number of volunteers who participated in the ﬁnal experimental results are summarized in the Figures 3–5 driving simulator experiment is limited, the results of driving (Tables 1–3). Figure 2 Schematic of experimental design 18 Safety effects of work zone advisory systems Journal of Intelligent and Connected Vehicles Suyi Mao et al. Volume 4 · Number 1 · 2021 · 16–27 Figure 3 Optimal lane change ratios by different DMS distance (3,000 vph) Figure 4 Optimal lane change ratios by different DMS distance (5,000 vph) It is observed from the experimental results that as the DMS from the work zone is smaller. However, GA is not the distance from the work zone becomes longer, the lane change algorithm to ﬁnd the global optimal solution. The optimal lane ratio of different subinterval becomes more evenly. It might change ratio that makes travel time variance the least may not infer that if there are more subintervals, the wider the range of be the optimal solution. But the approach used in this paper lane change options for drivers would be available. To ﬁnd a can explain the drivers’ lane change behaviors from the path with a shorter travel time, drivers may avoid changing perspective of the whole transportation system, which is closer lanes in a crowded place. Furthermore, it is not hard to ﬁnd to the real-world driving behaviors. The experimental results of that the longer the DMS distance is, the further the subinterval optimal lane change ratio are used to operate simulation when with maximum lane change ratio is from the work zone. This is evaluating the safety and efﬁciency of work zone advisory because, the closer the work zone, the higher the possibility of systems. time spent on changing lanes. Therefore, when there is a Experiment 1: In the traditional environment without CV, sufﬁcient distance gap for changing lanes, drivers will change TT , V , QT , DT and TTC varied in mean mean mean mean improved lanes in advance as soon as possible. But under different trafﬁc different trafﬁc volume and different DMS distance scenarios. volume conditions, the situation is different. As the trafﬁc ﬂow DMS is a traditional trafﬁc information delivery approach. increases, there are fewer opportunities to change lanes away According to the experimental results of optimal lane change from the work zone. Hence, when there is a trafﬁc congestion, ratio, different simulation experiments representing different the sum of lane change ratio including subintervals that far DMS distance scenarios are conducted. Three types of trafﬁc 19 Safety effects of work zone advisory systems Journal of Intelligent and Connected Vehicles Suyi Mao et al. Volume 4 · Number 1 · 2021 · 16–27 Figure 5 Optimal lane change ratios by different DMS distance (10,000 vph) Table 1 Optimal lane change ratios by different DMS distance (3,000 vph) DMS distance (m) Lane change ratio of subintervals (%) 400 29 71 600 14 21 65 1,000 34 18 34 10 4 1,400 23 11 21 2 26 8 9 1,800 19 19 12 6 8 20 6 4 6 2,200 14 5 13 7 13 4 16 13 6 6 3 2,600 41410 9 11 2 1 5 47101211 3,000 14 8 3 413 8 5 1 291310 1 81 Table 2 Optimal lane change ratios by different DMS distance (5,000 vph) DMS distance (m) Lane change ratio of subintervals (%) 400 47 53 600 39 58 3 1,000 31320 3232 1,400 20 11 13 2 24 8 22 1,800 15 11 7 10161110 2 18 2,200 712 6 8 1213 4 3101015 2,600 9335 19 14 19 11 17 3 15 3,000 10 0 11 5 7 5 10 11 1 5 1 11 10 7 6 Table 3 Optimal lane change ratios by different DMS distance (10,000 vph) DMS distance (m) Lane change ratio of subintervals (%) 400 36 64 600 78 13 9 1,000 24015 0 43 1,400 62028 7 713 19 1,800 23 7201312 5 12 4 4 2,200 11 11 14 9 5 11 7 7 10 8 7 2,600 914 9 14 1 7 0 81071119 3,000 929235 11 10 4 5 6 5 6 12 11 20 Safety effects of work zone advisory systems Journal of Intelligent and Connected Vehicles Suyi Mao et al. Volume 4 · Number 1 · 2021 · 16–27 volume (i.e. 3,000 vph, 5,000 vph and 10,000 vph) and eight immediately and some drivers will change lanes between DMS different DMS distances (i.e. 400 m, 600 m, 1,000 m, 1,400 m, and 200 m from the work zone. And the others will change 1,800 m, 2,200 m, 2,600 m and 3,000 m) are considered. The lanes just before the work zone. Because there is a trafﬁc following three examples demonstrate the lane-changing congestion, there are not enough opportunities for drivers to scenarios in different experiments. change lanes. Then, the lane change ratio of the subinterval One of the cases is shown in Figure 6, which represents the close to the work zone is still high. distance from DMS and work zone is 400 m and the trafﬁc Experiment 2: In the advanced environment with CV, CVs volume is 5,000 vph. Because the distance between DMS and that can receive trafﬁc information from in-vehicle warning work zone is very short, according to the results, it is inferred device earlier than manually driven vehicles can only receive that all the drivers will change lane immediately when they see trafﬁc information from DMS. It is assumed that the information displayed on DMS. construction warning of work zone is sent to CVs by the One of the cases shown in Figure 7, which represents the roadside device within 600 m ahead of DMS. Therefore, CV distance from DMS and work zone, is 600 m and the trafﬁc drivers were divided into more categories and some will change volume is 5,000 vph. Because the distance between DMS lanes ahead of the DMS. Figure 9 displays one of the and work zone is short, according to the results, it can be simulation scenarios when CV and MV are mixed in the road inferred that more than 90% of drivers will change lane network. when they have seen information displayed on DMS as soon The lane change ratios of manual vehicles (MVs) refer to the as possible. experimental results of the optimal lane change ratios. A new As it is shown in Figure 8, when the distance between DMS indicator named average safe lane-changing probability and work zone is more than 1 km, it was assumed that drivers (ASLP), which reﬂects the probability of making a safe lane are divided into three categories. Some drivers will change lanes change maneuver in the subinterval, was proposed. Figure 6 Distance between DMS and work zone is 400 m (5,000 vph) Figure 7 Distance between DMS and work zone is 600 m (5,000 vph) Figure 8 Distance between DMS and work zone is 1 km (5,000 vph) 21 Safety effects of work zone advisory systems Journal of Intelligent and Connected Vehicles Suyi Mao et al. Volume 4 · Number 1 · 2021 · 16–27 The calculation formula of ASLP is speciﬁed as follows: market penetration rates scenarios, the composition of lane subinterval changing ratios was recalculated and the market penetration rates of CV are increased successively. fs ðÞ it Different market penetration rates of CV (i.e. 0%, 30%, i¼1 ASLP ¼ (6) sub–interval 50%, 70% and 100%) were considered. There may be a phenomenon of information oversaturation because CV drivers will also see DMS. It was assumed that CV drivers will not 0 TTC < 1:5 approximation fs ¼ (7) respond to DMS, they only respond to the advanced roadside ðÞ it 1 TTC >¼ 1:5 approximation device. According to the results of Experiment 1, only one of the safest DMS distance scenarios was used in Experiment 2 x x 1 v 5 v 5 under each trafﬁc volume condition because it takes a long time L F L F TTC ¼ (8) approximation to run an experiment. v v F L where ASLP is the ASLP of a subinterval and i is the subinterval Results number of vehicle whose active lane is the right lane. In this Experiment 1: Figures 10–12 exhibit the simulation results of paper, there is only the possibility that vehicles in the right lane different trafﬁc volume scenarios in the traditional will change lanes because of the work zone layout. f (s ) is the it environment, respectively. Results represent the safety and safe lane-changing probability of a vehicle numbered i in the operational effects of placing DMS in different location. subinterval s at time t. n is the total number of vehicles. x is Figure 10 shows that it is more effective when the DMS is abscissa value of the leading vehicle in the right lane; x placed at 3 km in the upstream from the work zone considering is abscissa value of the following vehicle in the middle lane that efﬁciency and safety. The value of QT and DT is close mean mean is closest to the leading vehicle and it is in the middle lane; it is to 0. Because trafﬁc volume of this scenario is small, it indicates assumed that the leading vehicle’s lane changing maneuver will that the trafﬁc is very smooth. When under the condition of free last 5 s averagely; v is velocity of the following vehicle; and v F L ﬂow, the distance between DMS and work zone has little is velocity of the leading vehicle. inﬂuence on the efﬁciency of the whole trafﬁc environment (i.e. It is assumed that vehicles whose active lane is the right lane average delay time, average queue time, average speed and change lanes in the subinterval and calculate the TTC approximation travel time). This is because there are many opportunities to between these vehicles and the nearest vehicles close to them in change lanes, thus it is safer to place DMS far from work zone. the middle lane. If TTC is less than 1.5 s, the value of approximation It can avoid the concentration of the lane-changing behavior f(s ) is equal to 0, which indicates that it is not safe for the it that may cause more lateral conﬂicts. The lane-changing ratio vehicle to change lanes in the subinterval. If TTC is approximation is even in the interval, which indicates that drivers merge at more than 1.5 s, the value of f(s ) is equal to 1, which indicates it different subintervals evenly. When to change lanes depends on that it is safe for the vehicle to change lanes in the subinterval. drivers’ characteristics and their driving habit. However, if the According to the results of optimal lane change ratio, in the DMS placing distance is too short from the work zone, drivers beginning of the experiment, all MV’s data (location, speed, would not have enough space to change lanes, which may lead etc.) were collected to calculate the initial ASLP value of every to drivers’ aggressive merging maneuver, and it might cause subinterval. The value of ASLP in each subinterval is used as more conﬂicts when they are merging out from the right lane. the reference standard for the recommended lane-changing Figure 11 presents that it is more effective when the DMS is ratio for CV. The bigger the value of ASLP is, the subinterval placed 2.2 km upstream of the work zone considering safety. higher the lane-changing ratio in the subinterval will be. It is When under the condition of saturated ﬂow meaning that the assumed that CV’s compliance rate is 100%. In the ﬁrst loop, the lane-changing ratio referred to the ASLP of the trafﬁc is no longer smooth, long-distance DMS placed from the subinterval simulation scenario whose trafﬁc ﬂow composition is full of work zone may lead to lane-changing behaviors ahead of time. MV. And in the second loop, the recommended lane-changing However, it is not ideal for current trafﬁc conditions to meet the requirements of completing a lane-changing maneuver, which ratio referred to the ASLP calculated in the ﬁrst loop is subinterval is easy to cause more lateral conﬂicts between vehicles. send to CV. After simulation, the difference of ASLP subinterval between this loop and the previous loop is calculated. The loop Compared with the free ﬂow, the safest distance between DMS continues until this value is small enough. For different CV and work zone is shorter. Correspondingly, when the distance Figure 9 Schematic of CV and MV are mixed in the road network 22 Safety effects of work zone advisory systems Journal of Intelligent and Connected Vehicles Suyi Mao et al. Volume 4 · Number 1 · 2021 · 16–27 become longer, the negative inﬂuence on the safety and the safest distance DMS placed from the work zone is also efﬁciency of the whole trafﬁc system is more obvious. shorter. According to the results, a reasonable inference that it may lead Therefore, it can be concluded from the above results that to trafﬁc chaos if informed drivers too early when there is a when trafﬁc is relatively smooth, the location of DMS should be trafﬁc congestion can be made. far from the work zone, which not only improves the safety level Figure 12 presents that when the DMS is placed 1.0 km of the whole trafﬁc system, but also prevents affecting the upstream of the work zone, travel time is smallest, whereas efﬁciency of the whole trafﬁc system. The higher the value of N is not the smallest. Because of the heavy trafﬁc, trafﬁc volume is, the more obvious negative inﬂuence of long- TTC1.5 drivers will not have sufﬁcient opportunities to change lanes distance DMS placed from the work zone will have on the and they will keep driving forward until they have an efﬁciency and safety of the whole trafﬁc system. The best opportunity to change lanes, which might eventually cause distance DMS placed from the work zone should be trafﬁc congestion near the work zone. The safest distance DMS appropriately shortened when there is a trafﬁc congestion. placed from the work zone is 1.8 km in this scenario. Similarly, Figure 13 exhibits the safety and efﬁciency effects when compared with the scenario whose trafﬁc volume is 5,000 vph, DMS was placed at the safest distance from the work zone Figure 10 Safety and efﬁciency effects of DMS at 3,000 vph Figure 11 Safety and efﬁciency effects of DMS at 5,000 vph 23 Safety effects of work zone advisory systems Journal of Intelligent and Connected Vehicles Suyi Mao et al. Volume 4 · Number 1 · 2021 · 16–27 under different trafﬁc volume scenarios. The ﬁgure shows N varies greatly. Obviously, when the MPR is 100%, TTC1.5 that as trafﬁcvolumeincreases, crash risks increases, the value of N is smallest, which indicates that the TTC1.5 whereas trafﬁcefﬁciency of the whole trafﬁcsystem number of trafﬁcconﬂicts under the environment of full CV decreases, which is consistent with the common sense. is safest. The popularization of CV is a gradual process and different MPR of CV has to be considered during this Moreover, when trafﬁc volume increases, the safest distance between DMS and work zone is shorter, which is period. With the increase of the MPR of CV, the trafﬁc owing to the interaction between efﬁciency and safety level safety risks show volatility. When the MPR of CV is 50%, of the whole trafﬁcsystem. the value of N is greater than the value of N TTC1.5 TTC1.5 Experiment 2: Figures 14–16 exhibit the safety and efﬁciency under full MV environment, which revealed that the MPR of effects of different market penetration rates at different trafﬁc CV and trafﬁc safety risks do not conform to a simple linear volume scenarios (i.e. 3,000 vph, 5,000 vph and 10,000 vph) in relationship. the mixed advanced trafﬁc environment. Trafﬁcefﬁciency Figure 15 and 16 show that the safety and efﬁciency effect indicators and N representing the number of conﬂicts under different MPR when the trafﬁc volume is heavy. When TTC1.5 the MPR of CV is 100%, N is smallest, which indicates have been calculated. TTC1.5 As showninthe Figure 14, the value of indicators the scenarios is safest. With the increase of MPR of CV, the representing the efﬁciency of the whole trafﬁc system varies number of trafﬁcconﬂicts increase on the contrary in the slightly when trafﬁc volume is at 3,000 vph. It is worth beginning. It can be inferred that when there is serious trafﬁc noting that the value of QT and DT is close to 0, congestion, the advanced advisory system cannot work well. mean mean which is same with the results in Figure 10.As mentioned Because of the poor trafﬁc condition, there would be almost no earlier, the trafﬁc volume of these two scenarios is small. opportunities for drivers to change lanes even though they There is almost no queuing and delay. However, the value of receive the advanced information. Figure 12 Safety and efﬁciency effects of DMS at 10,000 vph Discussions of the results Figure 13 Safety and efﬁciency effects of DMS at different trafﬁc With the rapid development of information and volume communication technologies, more and more advanced equipment is put into application. The study identiﬁed that the improvement of efﬁciency and safety effects in the freeway construction scene by using advanced trafﬁc information delivery approaches. In the traditional environment using DMS to deliver warning information, the position and content inﬂuence drivers’ compliance rate. The safest distance DMS placed from the work zone is different under different trafﬁc condition (i.e. smooth, congested and supersaturated). When trafﬁc is relatively smooth, the location of DMS should be far from the work zone, which can not only improve the safety level of the whole trafﬁc system, but also avoid affecting the 24 Safety effects of work zone advisory systems Journal of Intelligent and Connected Vehicles Suyi Mao et al. Volume 4 · Number 1 · 2021 · 16–27 Figure 14 Safety and efﬁciency effects under different MPR at 3,000 vph Figure 15 Safety and efﬁciency effects under different MPR at 5,000 vph Figure 16 Safety and efﬁciency effects under different MPR at 10,000 vph 25 Safety effects of work zone advisory systems Journal of Intelligent and Connected Vehicles Suyi Mao et al. Volume 4 · Number 1 · 2021 · 16–27 efﬁciency of the whole trafﬁc system. However, the higher the and stable trafﬁc environment. It is worth noting that the MPR value of trafﬁc volume is, the more obvious negative inﬂuence of CV and trafﬁc safety risks do not conform to a simple linear of long distance DMS placed from the work zone will have on relationship. The introduction of CV into the whole trafﬁc the efﬁciency and safety of the whole trafﬁc system. It can be system is a complicated issue. The effect that CV will have on inferred that drivers did not have much opportunities to change the whole trafﬁc system is an urge key scientiﬁc problem that lanes because of the bad trafﬁc condition. Overlong distance for needs to be solved. It is worthy to note several limitations to this paper. First, lane changing will cause later conﬂicts of vehicles on the excessive information might be provided to some drivers contrary. Currently, many researchers agree that both because CV drivers will also see DMS information. Such efﬁciency and safety are of the top priority in the transportation information overload should be considered in follow-up system. A balance between pursuing efﬁciency and considering studies. Second, because this study used only microsimulation, safety should been found. The above results show that results do not reﬂect the real-world drivers’ reactions to DMS advanced communication technology in the CV environment and CV warning messages. And the objective of this research will greatly improve trafﬁcefﬁciency. However, the safety mainly focuses on V2I links by considering the connection effects near the work area does not conform to a simple rule, between infrastructure and vehicles under connected which may be affected by the structure of the road network, environment. vehicle-to-vehicle links will be considered in the trafﬁc conditions, the operation of advanced technology future study. A series of driving simulator experiments need to applications, the complex driving behaviors of drivers and so be conducted to capture the real driving behaviors so as to on. investigate the unresolved related issues. Human machine Furthermore, more detailed trafﬁc information provided in interface needs be used to simulate the process of in-vehicle the CV environment may lead to excessive information, which warning information delivery. Third, the validation of the might negatively affect drivers’ behavior. From the simulation model was not conducted because of the data experimental results above, with the increase of the MPR of limitation. Real data of each scenario should be collected for CV, the trafﬁc safety risks show volatility. When the MPR of validation and deep analysis to ensure the credibility of the CV is 50%, the value of N is more than it under total TTC1.5 experiment results. MV environment, which revealed that the MPR of CV and trafﬁc safety risks do not conform to a simple linear relationship. We can infer that when CV drivers receive References information earlier than non-CV drivers, CV drivers will change lanes earlier than them, there will cause more trafﬁc Abdulsattar, H., Mostaﬁzi, A. and Wang, H. (2018), conﬂicts because of the mixed trafﬁc ﬂow conditions. Because “Surrogate safety assessment of work zone rear-end of the increased lateral behaviors, the risk of collision will collisions in a connected vehicle environment: agent-based modeling framework”, Journal of Transportation Engineering, increase simultaneously. When the MPR of CV is 50%, the Part A: Systems, Vol. 144 No. 8, p. 4018038 level of confusion is highest. To improve the efﬁciency and Ardeshiri, A. and Jeihani, M. 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Journal of Intelligent and Connected Vehicles – Emerald Publishing
Published: Apr 26, 2021
Keywords: Connected vehicles; Driver behaviors and assistance; Intelligent vehicles; Vehicle dynamics and control; Vehicle-to-infrastructure communication (V2I); Work zone; Dynamic message sign (DMS); In-vehicle warning; Traffic simulation
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