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Modelling speed reduction behaviour on variable speed limit-controlled highways considering surrounding traffic pressure: a random parameters duration modelling approach

Variable speed limits are frequently used to improve traffic safety and harmonise traffic flow. This study investigates how, and to what extent, drivers reduce their speed upon passing a variable speed limit sign. We specifically consider the impact on braking behaviour due to the systematic inclusi...

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Main Authors: Yasir Ali, Mark PH Raadsen, Michiel CJ Bliemer
Format: Default Article
Published: 2023
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Online Access:https://hdl.handle.net/2134/25112117.v1
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author Yasir Ali
Mark PH Raadsen
Michiel CJ Bliemer
author_facet Yasir Ali
Mark PH Raadsen
Michiel CJ Bliemer
author_sort Yasir Ali (13768642)
collection Figshare
description Variable speed limits are frequently used to improve traffic safety and harmonise traffic flow. This study investigates how, and to what extent, drivers reduce their speed upon passing a variable speed limit sign. We specifically consider the impact on braking behaviour due to the systematic inclusion of different social pressures exerted by surrounding traffic. This social pressure is the natural result of having two vehicle cohorts created by a change in the variable speed limit (the new speed limit being higher than the original). The cohort with the higher speed limit overtakes vehicles with the lower speed limit, instigating a specific passing rate on drivers in the lower speed cohort. A driving simulator study is employed to obtain individual driver data whilst being able to systematically change the social pressure applied. A sample comprising sixty-seven participants conducted multiple randomised drives, with varying passing rates from as low as 90 veh/h to as high as 360 veh/h. The speed reduction behaviour of the participants is modelled using a random parameter duration modelling approach. Both the panel nature of the data and unobserved heterogeneity are captured through a correlated grouped random parameters with heterogeneity-in-the-mean model. The random parameters are predicated on the different passing rate scenarios, allowing drivers to take shorter or longer to reduce their speeds compared to the reference passing rate. It is shown that the extent of social pressure impacts braking behaviour and therefore affects safety measures, which is a function of the magnitude of the speed limit change. In addition, an extensive decision tree analysis is conducted to understand differential braking behaviour. Results reveal that, on average, female drivers take a shorter time to reduce their speed under a high passing rate but longer in a low passing rate scenario compared to males. Similarly, young drivers are found to take longer to reduce their speeds in a high passing rate scenario compared to other age groups. Our main findings indicate that the within-cohort safety is lowest under low passing rates due to comparatively larger speed differences between drivers. Yet, under a high passing rate, we observe an increase in violation of the speed limit by the lower speed limit vehicles (but less within cohort speed differences). Whilst normally this would be an undesired effect across cohorts, this violation is argued to lead to increased safety due to the smaller discrepancy in speed.
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spelling rr-article-251121172023-07-10T00:00:00Z Modelling speed reduction behaviour on variable speed limit-controlled highways considering surrounding traffic pressure: a random parameters duration modelling approach Yasir Ali (13768642) Mark PH Raadsen (17872580) Michiel CJ Bliemer (17872583) Transportation, logistics and supply chains Civil engineering Applied mathematics Passing rate Speed reduction Random parameters Duration model Heterogeneity Variable speed limits are frequently used to improve traffic safety and harmonise traffic flow. This study investigates how, and to what extent, drivers reduce their speed upon passing a variable speed limit sign. We specifically consider the impact on braking behaviour due to the systematic inclusion of different social pressures exerted by surrounding traffic. This social pressure is the natural result of having two vehicle cohorts created by a change in the variable speed limit (the new speed limit being higher than the original). The cohort with the higher speed limit overtakes vehicles with the lower speed limit, instigating a specific passing rate on drivers in the lower speed cohort. A driving simulator study is employed to obtain individual driver data whilst being able to systematically change the social pressure applied. A sample comprising sixty-seven participants conducted multiple randomised drives, with varying passing rates from as low as 90 veh/h to as high as 360 veh/h. The speed reduction behaviour of the participants is modelled using a random parameter duration modelling approach. Both the panel nature of the data and unobserved heterogeneity are captured through a correlated grouped random parameters with heterogeneity-in-the-mean model. The random parameters are predicated on the different passing rate scenarios, allowing drivers to take shorter or longer to reduce their speeds compared to the reference passing rate. It is shown that the extent of social pressure impacts braking behaviour and therefore affects safety measures, which is a function of the magnitude of the speed limit change. In addition, an extensive decision tree analysis is conducted to understand differential braking behaviour. Results reveal that, on average, female drivers take a shorter time to reduce their speed under a high passing rate but longer in a low passing rate scenario compared to males. Similarly, young drivers are found to take longer to reduce their speeds in a high passing rate scenario compared to other age groups. Our main findings indicate that the within-cohort safety is lowest under low passing rates due to comparatively larger speed differences between drivers. Yet, under a high passing rate, we observe an increase in violation of the speed limit by the lower speed limit vehicles (but less within cohort speed differences). Whilst normally this would be an undesired effect across cohorts, this violation is argued to lead to increased safety due to the smaller discrepancy in speed.<p></p> 2023-07-10T00:00:00Z Text Journal contribution 2134/25112117.v1 https://figshare.com/articles/journal_contribution/Modelling_speed_reduction_behaviour_on_variable_speed_limit-controlled_highways_considering_surrounding_traffic_pressure_a_random_parameters_duration_modelling_approach/25112117 CC BY 4.0
spellingShingle Transportation, logistics and supply chains
Civil engineering
Applied mathematics
Passing rate
Speed reduction
Random parameters
Duration model
Heterogeneity
Yasir Ali
Mark PH Raadsen
Michiel CJ Bliemer
Modelling speed reduction behaviour on variable speed limit-controlled highways considering surrounding traffic pressure: a random parameters duration modelling approach
title Modelling speed reduction behaviour on variable speed limit-controlled highways considering surrounding traffic pressure: a random parameters duration modelling approach
title_full Modelling speed reduction behaviour on variable speed limit-controlled highways considering surrounding traffic pressure: a random parameters duration modelling approach
title_fullStr Modelling speed reduction behaviour on variable speed limit-controlled highways considering surrounding traffic pressure: a random parameters duration modelling approach
title_full_unstemmed Modelling speed reduction behaviour on variable speed limit-controlled highways considering surrounding traffic pressure: a random parameters duration modelling approach
title_short Modelling speed reduction behaviour on variable speed limit-controlled highways considering surrounding traffic pressure: a random parameters duration modelling approach
title_sort modelling speed reduction behaviour on variable speed limit-controlled highways considering surrounding traffic pressure: a random parameters duration modelling approach
topic Transportation, logistics and supply chains
Civil engineering
Applied mathematics
Passing rate
Speed reduction
Random parameters
Duration model
Heterogeneity
url https://hdl.handle.net/2134/25112117.v1