How does an increased freeway speed limit influence the frequency of crashes on adjacent roads?

Alhomaidat, Fadi; Kwigizile, Valerian; Oh, Jun Seok; Houten, Ron Van

doi:10.1016/j.aap.2020.105433

Cited by 17 publications

(3 citation statements)

References 22 publications

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“…Interestingly, speeds either remained unchanged or decreased at the control sites across all quartiles and for both vehicle types. This is in contrast to prior research, which has suggested a potential spillover effect on adjacent roads (39).…”

Section: Figure 3 Plot Of Parameter Estimates For Speed Quantiles For Passenger Carcontrasting

confidence: 99%

Evaluating the Impacts of Speed Limit Increases on Rural Two-Lane Highways Using Quantile Regression

Mahmud

Gupta

Safaei

et al. 2021

Transportation Research Record: Journal of the Transportation R

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Understanding speed selection behavior of drivers following speed limit increases is critically important. To date, the literature has largely focused on freeways and the effects of speed limit changes on two-lane highways remains under researched. Prior research has generally focused on changes to mean speeds, although the speeds of both the highest and lowest drivers are also of great interest. This study investigates trends in free-flow travel speeds following 2017 legislation that increased the posted speed limit from 55 to 65 mph on 943 mi of rural highways in Michigan. Speed data were collected for over 46,000 drivers at 67 increase segments where speed limit increased and 28 control segments where speed limits remained unchanged, before and during each of the two successive years following the speed limit increases. Site-specific traffic, geometric, and cross-sectional information was also collected. Impacts of the speed limit increases on the 15th, 50th, and 85th percentile speeds were evaluated using quantile regression. Separate analyses were conducted for passenger cars and heavy vehicles. Locations where the speed limits were raised experienced increases in travel speeds ranging from 2.8 to 4.8 mph. The control sites experienced marginal changes in speeds, which suggests that any spillover effects of the higher speed limits have been limited. Significant differences were observed across the quantiles with respect to the effects of the speed limit increases, as well as numerous site-specific variables of interest. The results provide important insights about the nature of driver speed selection and the impacts of speed limit increases.

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Section: Figure 3 Plot Of Parameter Estimates For Speed Quantiles For Passenger Carcontrasting

confidence: 99%

Evaluating the Impacts of Speed Limit Increases on Rural Two-Lane Highways Using Quantile Regression

Mahmud

Gupta

Safaei

et al. 2021

Transportation Research Record: Journal of the Transportation R

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show abstract

“…In that regard, several studies have demonstrated the positive exponential relationship between the speed limit and crashes ( 37 , 68–70 ). In alignment with this study, the previous study of Alhomaidat et al ( 71 ) indicated a 13.9 percent increase in arterial road crash frequency as a result of 5 mph increase in adjacent freeway speed limits. Furthermore, the spillover effect in speed limit can be grasped by the fundamental traffic flow relationship between congestion and speed.…”

Section: Discussionsupporting

confidence: 87%

Segment-Level Spatial Spillover Effects of Exogenous Characteristics of Arterials on Crash Frequency

Atumo

Zhang²,

et al. 2023

Transportation Research Record: Journal of the Transportation R

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Studies of spatial effects on road traffic safety are highly skewed in relation to aggregation units. As a result, the spatial effect of road traffic crashes at segment-level aggregation is rarely investigated. In light of that, this study investigates spatial spillover effects to determine the effects of independent variable changes initiated in one segment on the dependent variable of its neighboring segments. Additionally, the performance of the implemented models is evaluated under five different spatial weighting approaches. Spatial spillover effect of fatal and injury crashes aggregated at the segment level is estimated with the spatial lag of explanatory variables model under the general framework of Poisson and negative binomial models. The results indicate (i) spatial spillover effects are better modeled with spatial relation conceptualized by inverse distance spatial weighting schemes; (ii) spatial lag of explanatory variables under negative binomial and inverse distance spatial weighting provides the best model fitting; (iii) exogenous interactions among influence factors of fatal and injury crashes have a noteworthy effect in determining the crash frequency of neighboring segments. Convincingly, spatial spillover effect seems to significantly affect the results of conventional count modeling at the segment levels. To that effect, this study expects to provide empirical evidence and complement the existing literature on the impact of changes in explanatory variables initiated in a given segment on the safety of segments in proximity.

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“…In the literature, there are studies whose conclusions are somewhat opposed. Although some research found that speed limit reductions sometimes have an insignificant effect on crash frequencies (Parker, 1997;Vernon et al, 2004;Chen et al, 2013), many others indicate that the raised speed limits contribute to an increase in total crashes (Kockelman et al, 2006;Kwayu et al, 2020;Alhomaidat et al, 2020). Contrarily, Tagar and Pulugurtha (2021a) observed a decrease in the total, non-incapacitating and possible injury, and property damage only crash frequencies at entry ramp speed-change lanes after the increase in the freeway-posted speed limit.…”

Section: Incidence Of Speed Limit Changesmentioning

confidence: 99%

Exploring Traffic Speed Patterns for the Implementation of Variable Speed Limit (VSL) Signs

Kalambay,

Pulugurtha

2023

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Traffic congestion is a prevalent issue during peak travel hours on roads in the United States. This study focuses on identifying suitable road links in Charlotte, North Carolina, for implementing variable speed limit (VSL) signs. Real-world traffic speed data collected over one year was analyzed to identify specific road links with favorable characteristics for VSL sign installations. The analysis considered weekdays, weekends, and specific times of the day to capture variations in speed patterns. The results revealed that roads with lower speed limits consistently experienced speeds exceeding the posted speed limits, suggesting additional enforcement or safety measures. For roads with higher speed limits, mean speeds were generally close to the speed limits, but the 85th percentile speeds exceeded them, indicating a potential need for speed management measures. Road links with a 45/50 mph speed limit display a unique pattern compared to other clusters. The mean speed on these roads decreases as the standard deviation increases. The findings contribute to understanding traffic speed patterns and provide valuable insights for transportation planning and management.

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How does an increased freeway speed limit influence the frequency of crashes on adjacent roads?

Cited by 17 publications

References 22 publications

Evaluating the Impacts of Speed Limit Increases on Rural Two-Lane Highways Using Quantile Regression

Evaluating the Impacts of Speed Limit Increases on Rural Two-Lane Highways Using Quantile Regression

Segment-Level Spatial Spillover Effects of Exogenous Characteristics of Arterials on Crash Frequency

Exploring Traffic Speed Patterns for the Implementation of Variable Speed Limit (VSL) Signs

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