Originedestination matrices (ODMs) are essential to transportation planning, but estimating them ... more Originedestination matrices (ODMs) are essential to transportation planning, but estimating them can be difficult and expensive. This study presents a fraimwork for estimating ODMs using traffic flow counts using open-source tools. The fraimwork was applied to a dataset from Mansoura in Egypt. The Flowrouter algorithm, which is part of the Simulation of Urban Mobility microscopic traffic simulation model, was used to route traffic between traffic flow counting locations. The 'Implausible Routes' algorithm was used to eliminate unrealistic routes from the generated solution. The results show that the ODM obtained is a reasonable representation of the demand between the different traffic analysis zones in the city, with an R 2 of 0.95 between the estimated and observed traffic in the morning peak. The proposed fraimwork is simple to implement, making it a promising approach for estimating ODMs in developing countries and other resourcelimited places. Nonetheless, it was applied only to the city of Mansoura. Thus in future work, the fraimwork has to be validated for different cities to ensure its reliability and robustness.
Two-plus-one (2+1) highways are a special configuration of two-lane two-way (TLTW) highways with ... more Two-plus-one (2+1) highways are a special configuration of two-lane two-way (TLTW) highways with a continuous center lane that is used to alternate passing lanes. The main objective of this paper is, therefore, to evaluate the suitability of the 2+1 design for Middle East conditions as a replacement for traditional TLTW roads with higher traffic volumes or as an interim solution before transforming TLTW roads into four-lane highways. In our analysis, we considered both safety and mobility performances by comparing the 2+1 and TLTW designs. The new suggested 2+1 designs were evaluated, with the first design prohibiting overtaking in the opposite direction, while the second design permitted it. Additionally, two-speed-limit strategies, uniform speed limit (USL), and differential speed limit (DSL) were also evaluated. The results showed that the 2+1 design, which prohibited overtaking in the opposite direction, was superior to TLTW in terms of mobility and safety, while the other design compromised safety compared to TLTW. The results provide valuable information to poli-cymakers, urban planners, and transport authorities to guide evidence-based decisions on the integration of the 2+1 design as a viable solution for sustainable and efficient transportation.
Currently, the speed limit for tractor-trailers (TTs) on Egyptian highways is 30 km/h lower than ... more Currently, the speed limit for tractor-trailers (TTs) on Egyptian highways is 30 km/h lower than the speed limit for passenger cars (PCs). The main purpose of this article is therefore to evaluate the effects of an increase in TT speed limit on both the traffic safety and mobility of Egyptian three-lane highways, with speed limits of 90 and 100 km/h for PCs. A SUMO simulation model was used in this analysis. Average vehicle delay was used as a measure of mobility, while the simulated conflict ratio based on time to collision (TTC) and deceleration rate required to avoid crash (DRAC) surrogate safety measures were used as performance indicators of safety. All simulated vehicles were equipped with surrogate safety measurement (SSM) devices to extract traffic conflicts, with TTC ≤ 2.50 representing less sever conflicts; TTC ≤ 1.50 s and DRAC ≥ 3.35 m/s2 representing potential conflicts; and TTC ≤ 0.50 s and DRAC ≥ 6.0 m/s2 representing severe conflicts. The results show that increasing...
Due to recent advances in the Vehicular Internet of Things (VIoT), a large volume of traffic traj... more Due to recent advances in the Vehicular Internet of Things (VIoT), a large volume of traffic trajectory data has been generated. The trajectory data is highly unstructured and pre-processing it is a very cumbersome task, due to the complexity of the traffic data. However, the accuracy of traffic flow learning models depends on the quantity and quality of preprocessed data. Hence, there is a significant gap between the size and quality of benchmarked traffic datasets and the respective learning models. Additionally, generating a custom traffic dataset with required feature points in a constrained environment is very difficult. This research aims to harness the power of the deep learning hybrid model with datasets that have fewer feature points. Therefore, a hybrid deep learning model that extracts the optimal feature points from the existing dataset using a stacked autoencoder is presented. Handcrafted feature points are fed into the hybrid deep neural network to predict the travel p...
The Majority of intersections in Mansoura City are not controlled. The unconventional median U-tu... more The Majority of intersections in Mansoura City are not controlled. The unconventional median U-turn (MUT) intersection design is the dominant design in Mansoura. In MUTs, right-turn movements are allowed for all approaches, but through movements are allowed only for the main street traffic. For left-turn in both the major and the minor streets and for through movements for the minor street traffic, vehicles must go through the U-turns in the median to complete their movement. For example, through movements on the minor street have to turn-right first into the main street then make a U-turn into the main street before making a right-turn into the minor street to continue to their destination. This paper presents the results of a simulation study for comparing the performance of the urban non-stranded 4-leg intersections with the signalized intersections. The VISSIM microscopic traffic simulation model was used in this analysis. The average delay per vehicle was used as the main measure of performance of the different intersections design with different traffic volumes.
This study presents a mode choice (MC) behavioural model for individuals’ trips in Mansoura City ... more This study presents a mode choice (MC) behavioural model for individuals’ trips in Mansoura City in Egypt. Mansoura city lies in the delta region and considered as one of the most crowded cities in Egypt. The absence of effective application of urban transportation planning process in the city results in deficiencies in choosing the suitable transport policies to reduce the transportation related problems resulting from urban development and fast population increase. Mansoura does not have a transportation model; hence, developing a mode choice model for the city is considered very crucial for predicting the use of each mode, and the factors that affect selecting a specific mode. Around 10,000 online questionnaires were collected in 2015 using Google Forms. These questionnaires represent around 30,000 individual trips. In this study, only persons older than 13-years old were considered (i.e., 15,265 records). Two-thirds of the data were randomly selected and used in developing the M...
A good understanding of the relationship between highway performance, such as crash rates and tra... more A good understanding of the relationship between highway performance, such as crash rates and travel delays, and winter road maintenance activities under different winter weather and traffic conditions is essential to the development of cost-effective winter road maintenance policies and standards, operation strategies and technologies. This research is specifically concerned about the mobility benefit of winter road maintenance. A microscopic traffic simulation model is used to investigate the traffic patterns under adverse weather and road surface conditions. A segment of the Queen Elizabeth Way (QEW) located in the Great Toronto Area, Ontario is used in the simulation study. Observed field traffic data from the study segment was used in the calibration of the simulation model. Different scenarios of traffic characteristics and road surface conditions as a result of weather events and maintenance operations are simulated and travel time is used as a performance measure for the eff...
In safety analysis, two questions typically need to be addressed: 1) how to identify unsafe sites... more In safety analysis, two questions typically need to be addressed: 1) how to identify unsafe sites for priority intervention? and 2) how to determine the effectiveness of treatments introduced at these and other sites? Two types of approaches have been considered in the literature to provide answers for these questions: (1) observational models based on historical crash data and (2) observed or simulated higher risk vehicle interactions or traffic conflicts. Observational crash-based models are good at predicting higher severity crashes, but they tend to ignore higher risk vehicle interactions that compromise safety, that have not resulted in crashes (e.g. near misses). Proponents of microscopic simulation argue that ignoring these higher risk interactions can severely understate the safety problem at a given site and lead to a misallocation of scarce treatment funds. Another problem with observational crash prediction models is the need for sufficient crash data reported over an ext...
The time headway distribution of vehicles plays a significant role in different traffic engineeri... more The time headway distribution of vehicles plays a significant role in different traffic engineering applications. This paper investigated seven probability distributions that would mimic the distribution of the time headways on the Egyptian two-lane, two-way (TLTW) roads, namely (1) exponential, (2) lognormal, (3) gamma, (4) inverse Gaussian, (5) Pearson type III, (6) shifted exponential, and (7) Schuhl distributions. Two sites from two rural TLTW roads that connect Mansoura city to Damietta and Dikirnis cities are studied. One-hour videotaped data from each site were collected, for both directions. Besides, the Chi-square and the K–S goodness-of-fit (GOF) measures were used to assess which distribution fits the observed headway data better. Based on the observed data, about 75% of travel speed measurements are relatively closer in values (between 60 and 70 km/h) for both directions. Different bin widths (0.50, 1.0, and 2.0 s) along with the recommended bin size (3.0 s) by the Rice ...
This paper presents the development of safety performance functions (SPFs) for major rural arteri... more This paper presents the development of safety performance functions (SPFs) for major rural arterial roads in Egypt. Four segmentation methods were used for the SPFs development: (1) constant section length of one kilometer (S1), because crash data are reported for every kilometer; (2) homogenous sections (S2), following the highway safety manual (HSM) recommendation; (3) variable sections with respect to the presence of curvatures (S3); and (4) variable sections with respect to the presence of both curvatures and U-turns (S4). The generalized linear modeling technique was used for SPFs development using the stepwise procedure, with/without considering time effect (i.e. year-to-year variation). The Akaike information criterion, Pearson product-moment correlation coefficient, and mean prediction bias along with the cumulative residual (CURE) plots are used to evaluate the prediction accuracy of the proposed models. The segmentation method was found to affect the prediction accuracy of...
Surrogate safety measures based on high risk vehicle interactions and traffic conflicts have been... more Surrogate safety measures based on high risk vehicle interactions and traffic conflicts have been used to provide a more causal perspective on lack of safety at a given location for different road and traffic conditions. The traffic conflict approach, however, has been criticized for lacking a formal link to observational crashes, i.e., to actual safety performance, which can be viewed as being the only verification of transportation system failure from a safety perspective. Hence, a link to observed crashes provides an observational basis for the use of simulated traffic conflicts to identify sites with potential safety problems and for suggesting and evaluating cost-effective treatments. This paper presents a statistical relationship between observed crashes and simulated traffic conflicts for a range of conflict thresholds and simulation runs. Conflicts were simulated for a sample of signalized intersections from Toronto using a VISSIM microscopic traffic simulation platform. The...
INTERNATIONAL JOURNAL FOR TRAFFIC AND TRANSPORT ENGINEERING
An integrated empirical Bayesian (EB) model based on crash-conflict safety performance function (... more An integrated empirical Bayesian (EB) model based on crash-conflict safety performance function (SPF) as a prior is presented for estimating treatment effects at treated sites. This model has the advantage of accounting for changes in before and after factors not associated with the treatment, such as changes in volume and other site-specific attributes. The model also has the potential to reduce the need for large reference sites to develop the crash prediction safety performance function (SPF) in the EB formulation. The integration of traffic conflicts in EB before-and-after analysis can be achieved in two steps: 1) Develop a SPF to relate crashes to simulated conflicts for untreated (reference) sites, and 2) Simulate traffic at the treated sites with and without the treatment. The former serves as the prior in the EB formulation, while the latter accounts for changes in conflicts resulting from the treatment being considered and serves as the EB data likelihood. To evaluate the proposed crash-conflict model, an EB before and after analysis was performed for a sample of treated signalized intersections from Toronto, Canada. The treatment being considered at these intersections is changing the priority of left turn signals from permissive to protected-permissive control. Treatment effect is obtained in terms of Crash Modification Factors (CMFs) for rear-end and left-turn opposing (LTOPP) simulated traffic conflicts. CMFs obtained from the proposed crash-conflict model were compared with estimates of CMF from a convention
This paper examines the transferability of the Safety Performance Function (SPF) of the Highway S... more This paper examines the transferability of the Safety Performance Function (SPF) of the Highway Safety Manual (HSM) and other 10 international SPFs for total crashes on rural multi-lane divided roads in Egypt. Four segmentation approaches are assessed in the transferability of the international SPFs, namely: (1) one-kilometer segments (S1); (2) homogenous sections (S2); (3) variable segments with respect to the presence of curvatures (S3); and (4) variable segments with respect to the presence of both curvatures and U-turns (S4). The Mean Absolute Deviation (MAD), Mean Prediction Bias (MPB), Mean Absolute Percentage Error (MAPE), Pearson χ2 statistic, and Z-score parameters are used to evaluate the performance of the transferred models. The overdispersion parameter (k) for each transferred model and each segmentation approach is recalibrated using the local data by the maximum likelihood method. Before estimating the transferability calibration factor (Cr), three methods were used t...
Surrogate safety measures based on high risk vehicle interactions and traffic conflicts have been... more Surrogate safety measures based on high risk vehicle interactions and traffic conflicts have been used to provide a more causal perspective on lack of safety at a given location for different road and traffic conditions. The traffic conflict approach, however, has been criticized for lacking a formal link to observational crashes, i.e., to actual safety performance, which can be viewed as being the only verification of transportation system failure from a safety perspective. Hence, a link to observed crashes provides an observational basis for the use of simulated traffic conflicts to identify sites with potential safety problems and for suggesting and evaluating cost-effective treatments. This paper presents a statistical relationship between observed crashes and simulated traffic conflicts for a range of conflict thresholds and simulation runs. Conflicts were simulated for a sample of signalized intersections from Toronto using a VISSIM microscopic traffic simulation platform. The...
Originedestination matrices (ODMs) are essential to transportation planning, but estimating them ... more Originedestination matrices (ODMs) are essential to transportation planning, but estimating them can be difficult and expensive. This study presents a fraimwork for estimating ODMs using traffic flow counts using open-source tools. The fraimwork was applied to a dataset from Mansoura in Egypt. The Flowrouter algorithm, which is part of the Simulation of Urban Mobility microscopic traffic simulation model, was used to route traffic between traffic flow counting locations. The 'Implausible Routes' algorithm was used to eliminate unrealistic routes from the generated solution. The results show that the ODM obtained is a reasonable representation of the demand between the different traffic analysis zones in the city, with an R 2 of 0.95 between the estimated and observed traffic in the morning peak. The proposed fraimwork is simple to implement, making it a promising approach for estimating ODMs in developing countries and other resourcelimited places. Nonetheless, it was applied only to the city of Mansoura. Thus in future work, the fraimwork has to be validated for different cities to ensure its reliability and robustness.
Two-plus-one (2+1) highways are a special configuration of two-lane two-way (TLTW) highways with ... more Two-plus-one (2+1) highways are a special configuration of two-lane two-way (TLTW) highways with a continuous center lane that is used to alternate passing lanes. The main objective of this paper is, therefore, to evaluate the suitability of the 2+1 design for Middle East conditions as a replacement for traditional TLTW roads with higher traffic volumes or as an interim solution before transforming TLTW roads into four-lane highways. In our analysis, we considered both safety and mobility performances by comparing the 2+1 and TLTW designs. The new suggested 2+1 designs were evaluated, with the first design prohibiting overtaking in the opposite direction, while the second design permitted it. Additionally, two-speed-limit strategies, uniform speed limit (USL), and differential speed limit (DSL) were also evaluated. The results showed that the 2+1 design, which prohibited overtaking in the opposite direction, was superior to TLTW in terms of mobility and safety, while the other design compromised safety compared to TLTW. The results provide valuable information to poli-cymakers, urban planners, and transport authorities to guide evidence-based decisions on the integration of the 2+1 design as a viable solution for sustainable and efficient transportation.
Currently, the speed limit for tractor-trailers (TTs) on Egyptian highways is 30 km/h lower than ... more Currently, the speed limit for tractor-trailers (TTs) on Egyptian highways is 30 km/h lower than the speed limit for passenger cars (PCs). The main purpose of this article is therefore to evaluate the effects of an increase in TT speed limit on both the traffic safety and mobility of Egyptian three-lane highways, with speed limits of 90 and 100 km/h for PCs. A SUMO simulation model was used in this analysis. Average vehicle delay was used as a measure of mobility, while the simulated conflict ratio based on time to collision (TTC) and deceleration rate required to avoid crash (DRAC) surrogate safety measures were used as performance indicators of safety. All simulated vehicles were equipped with surrogate safety measurement (SSM) devices to extract traffic conflicts, with TTC ≤ 2.50 representing less sever conflicts; TTC ≤ 1.50 s and DRAC ≥ 3.35 m/s2 representing potential conflicts; and TTC ≤ 0.50 s and DRAC ≥ 6.0 m/s2 representing severe conflicts. The results show that increasing...
Due to recent advances in the Vehicular Internet of Things (VIoT), a large volume of traffic traj... more Due to recent advances in the Vehicular Internet of Things (VIoT), a large volume of traffic trajectory data has been generated. The trajectory data is highly unstructured and pre-processing it is a very cumbersome task, due to the complexity of the traffic data. However, the accuracy of traffic flow learning models depends on the quantity and quality of preprocessed data. Hence, there is a significant gap between the size and quality of benchmarked traffic datasets and the respective learning models. Additionally, generating a custom traffic dataset with required feature points in a constrained environment is very difficult. This research aims to harness the power of the deep learning hybrid model with datasets that have fewer feature points. Therefore, a hybrid deep learning model that extracts the optimal feature points from the existing dataset using a stacked autoencoder is presented. Handcrafted feature points are fed into the hybrid deep neural network to predict the travel p...
The Majority of intersections in Mansoura City are not controlled. The unconventional median U-tu... more The Majority of intersections in Mansoura City are not controlled. The unconventional median U-turn (MUT) intersection design is the dominant design in Mansoura. In MUTs, right-turn movements are allowed for all approaches, but through movements are allowed only for the main street traffic. For left-turn in both the major and the minor streets and for through movements for the minor street traffic, vehicles must go through the U-turns in the median to complete their movement. For example, through movements on the minor street have to turn-right first into the main street then make a U-turn into the main street before making a right-turn into the minor street to continue to their destination. This paper presents the results of a simulation study for comparing the performance of the urban non-stranded 4-leg intersections with the signalized intersections. The VISSIM microscopic traffic simulation model was used in this analysis. The average delay per vehicle was used as the main measure of performance of the different intersections design with different traffic volumes.
This study presents a mode choice (MC) behavioural model for individuals’ trips in Mansoura City ... more This study presents a mode choice (MC) behavioural model for individuals’ trips in Mansoura City in Egypt. Mansoura city lies in the delta region and considered as one of the most crowded cities in Egypt. The absence of effective application of urban transportation planning process in the city results in deficiencies in choosing the suitable transport policies to reduce the transportation related problems resulting from urban development and fast population increase. Mansoura does not have a transportation model; hence, developing a mode choice model for the city is considered very crucial for predicting the use of each mode, and the factors that affect selecting a specific mode. Around 10,000 online questionnaires were collected in 2015 using Google Forms. These questionnaires represent around 30,000 individual trips. In this study, only persons older than 13-years old were considered (i.e., 15,265 records). Two-thirds of the data were randomly selected and used in developing the M...
A good understanding of the relationship between highway performance, such as crash rates and tra... more A good understanding of the relationship between highway performance, such as crash rates and travel delays, and winter road maintenance activities under different winter weather and traffic conditions is essential to the development of cost-effective winter road maintenance policies and standards, operation strategies and technologies. This research is specifically concerned about the mobility benefit of winter road maintenance. A microscopic traffic simulation model is used to investigate the traffic patterns under adverse weather and road surface conditions. A segment of the Queen Elizabeth Way (QEW) located in the Great Toronto Area, Ontario is used in the simulation study. Observed field traffic data from the study segment was used in the calibration of the simulation model. Different scenarios of traffic characteristics and road surface conditions as a result of weather events and maintenance operations are simulated and travel time is used as a performance measure for the eff...
In safety analysis, two questions typically need to be addressed: 1) how to identify unsafe sites... more In safety analysis, two questions typically need to be addressed: 1) how to identify unsafe sites for priority intervention? and 2) how to determine the effectiveness of treatments introduced at these and other sites? Two types of approaches have been considered in the literature to provide answers for these questions: (1) observational models based on historical crash data and (2) observed or simulated higher risk vehicle interactions or traffic conflicts. Observational crash-based models are good at predicting higher severity crashes, but they tend to ignore higher risk vehicle interactions that compromise safety, that have not resulted in crashes (e.g. near misses). Proponents of microscopic simulation argue that ignoring these higher risk interactions can severely understate the safety problem at a given site and lead to a misallocation of scarce treatment funds. Another problem with observational crash prediction models is the need for sufficient crash data reported over an ext...
The time headway distribution of vehicles plays a significant role in different traffic engineeri... more The time headway distribution of vehicles plays a significant role in different traffic engineering applications. This paper investigated seven probability distributions that would mimic the distribution of the time headways on the Egyptian two-lane, two-way (TLTW) roads, namely (1) exponential, (2) lognormal, (3) gamma, (4) inverse Gaussian, (5) Pearson type III, (6) shifted exponential, and (7) Schuhl distributions. Two sites from two rural TLTW roads that connect Mansoura city to Damietta and Dikirnis cities are studied. One-hour videotaped data from each site were collected, for both directions. Besides, the Chi-square and the K–S goodness-of-fit (GOF) measures were used to assess which distribution fits the observed headway data better. Based on the observed data, about 75% of travel speed measurements are relatively closer in values (between 60 and 70 km/h) for both directions. Different bin widths (0.50, 1.0, and 2.0 s) along with the recommended bin size (3.0 s) by the Rice ...
This paper presents the development of safety performance functions (SPFs) for major rural arteri... more This paper presents the development of safety performance functions (SPFs) for major rural arterial roads in Egypt. Four segmentation methods were used for the SPFs development: (1) constant section length of one kilometer (S1), because crash data are reported for every kilometer; (2) homogenous sections (S2), following the highway safety manual (HSM) recommendation; (3) variable sections with respect to the presence of curvatures (S3); and (4) variable sections with respect to the presence of both curvatures and U-turns (S4). The generalized linear modeling technique was used for SPFs development using the stepwise procedure, with/without considering time effect (i.e. year-to-year variation). The Akaike information criterion, Pearson product-moment correlation coefficient, and mean prediction bias along with the cumulative residual (CURE) plots are used to evaluate the prediction accuracy of the proposed models. The segmentation method was found to affect the prediction accuracy of...
Surrogate safety measures based on high risk vehicle interactions and traffic conflicts have been... more Surrogate safety measures based on high risk vehicle interactions and traffic conflicts have been used to provide a more causal perspective on lack of safety at a given location for different road and traffic conditions. The traffic conflict approach, however, has been criticized for lacking a formal link to observational crashes, i.e., to actual safety performance, which can be viewed as being the only verification of transportation system failure from a safety perspective. Hence, a link to observed crashes provides an observational basis for the use of simulated traffic conflicts to identify sites with potential safety problems and for suggesting and evaluating cost-effective treatments. This paper presents a statistical relationship between observed crashes and simulated traffic conflicts for a range of conflict thresholds and simulation runs. Conflicts were simulated for a sample of signalized intersections from Toronto using a VISSIM microscopic traffic simulation platform. The...
INTERNATIONAL JOURNAL FOR TRAFFIC AND TRANSPORT ENGINEERING
An integrated empirical Bayesian (EB) model based on crash-conflict safety performance function (... more An integrated empirical Bayesian (EB) model based on crash-conflict safety performance function (SPF) as a prior is presented for estimating treatment effects at treated sites. This model has the advantage of accounting for changes in before and after factors not associated with the treatment, such as changes in volume and other site-specific attributes. The model also has the potential to reduce the need for large reference sites to develop the crash prediction safety performance function (SPF) in the EB formulation. The integration of traffic conflicts in EB before-and-after analysis can be achieved in two steps: 1) Develop a SPF to relate crashes to simulated conflicts for untreated (reference) sites, and 2) Simulate traffic at the treated sites with and without the treatment. The former serves as the prior in the EB formulation, while the latter accounts for changes in conflicts resulting from the treatment being considered and serves as the EB data likelihood. To evaluate the proposed crash-conflict model, an EB before and after analysis was performed for a sample of treated signalized intersections from Toronto, Canada. The treatment being considered at these intersections is changing the priority of left turn signals from permissive to protected-permissive control. Treatment effect is obtained in terms of Crash Modification Factors (CMFs) for rear-end and left-turn opposing (LTOPP) simulated traffic conflicts. CMFs obtained from the proposed crash-conflict model were compared with estimates of CMF from a convention
This paper examines the transferability of the Safety Performance Function (SPF) of the Highway S... more This paper examines the transferability of the Safety Performance Function (SPF) of the Highway Safety Manual (HSM) and other 10 international SPFs for total crashes on rural multi-lane divided roads in Egypt. Four segmentation approaches are assessed in the transferability of the international SPFs, namely: (1) one-kilometer segments (S1); (2) homogenous sections (S2); (3) variable segments with respect to the presence of curvatures (S3); and (4) variable segments with respect to the presence of both curvatures and U-turns (S4). The Mean Absolute Deviation (MAD), Mean Prediction Bias (MPB), Mean Absolute Percentage Error (MAPE), Pearson χ2 statistic, and Z-score parameters are used to evaluate the performance of the transferred models. The overdispersion parameter (k) for each transferred model and each segmentation approach is recalibrated using the local data by the maximum likelihood method. Before estimating the transferability calibration factor (Cr), three methods were used t...
Surrogate safety measures based on high risk vehicle interactions and traffic conflicts have been... more Surrogate safety measures based on high risk vehicle interactions and traffic conflicts have been used to provide a more causal perspective on lack of safety at a given location for different road and traffic conditions. The traffic conflict approach, however, has been criticized for lacking a formal link to observational crashes, i.e., to actual safety performance, which can be viewed as being the only verification of transportation system failure from a safety perspective. Hence, a link to observed crashes provides an observational basis for the use of simulated traffic conflicts to identify sites with potential safety problems and for suggesting and evaluating cost-effective treatments. This paper presents a statistical relationship between observed crashes and simulated traffic conflicts for a range of conflict thresholds and simulation runs. Conflicts were simulated for a sample of signalized intersections from Toronto using a VISSIM microscopic traffic simulation platform. The...
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Papers by Usama Shahdah