Speed Limit Reduction Research Articles

Built environmental correlates of cycling for transport across Europe

This cross-sectional study aimed to determine which objective built environmental factors, identified using a virtual neighbourhood audit, were associated with cycling for transport in adults living in five urban regions across Europe. The moderating role of age, gender, socio-economic status and country on these associations was also investigated. Overall, results showed that people living in neighbourhoods with a preponderance of speed limits below 30km/h, many bicycle lanes, with less traffic calming devices, more trees, more litter and many parked cars forming an obstacle on the road were more likely to cycle for transport than people living in areas with lower prevalence of these factors. Evidence was only found for seven out of 56 possible moderators of these associations. These results suggest that reducing speed limits for motorized vehicles and the provision of more bicycle lanes may be effective interventions to promote cycling in Europe.

Going Fast or Going Green? Evidence from Environmental Speed Limits in Norway

This paper studies the impact of speed limits on local air pollution using a series of datespecific speed limit reductions in Oslo over the 2004-2011 period. We find that lowering the speed limit from 80 to 60 km/h reduces travel speed by 5.8 km/h. However, we find no evidence of reduced air pollution as measured next to the treated roads. Our estimates suggest an annual time loss of the speed limit reductions of 55 USD per affected vehicle. Our findings imply that policy makers need to consider other actions than speed limit reductions to improve local air quality.

Variable Speed Limit Study Upstream of an Indiana Work Zone with Vehicle Matching

Traffic management in work zones presents significant mobility and safety challenges for agencies. The goals of a work zone traffic management plan are to safely slow vehicles ahead of the work zone, maintain speeds that provide for the safety of motorists and construction workers, and manage the growth of queues. Historically, variable speed limits (VSLs) have been presented as a form of technology that can dynamically regulate speed in response to prevailing traffic conditions. However, techniques used to evaluate the impact of VSLs typically use aggregated statistics such as mean and standard deviation to determine the typical speed reduction. This paper presents a new methodology to evaluate the impact of VSL signage on the basis of individual vehicle matching. The speeds and speed changes of these matched vehicles were used to analyze individual driver response to the VSLs. This approach allows agencies to understand the impact that VSL signage has on the distribution of vehicle speeds. It was concluded that vehicles would need to observe multiple signs before any tangible reduction in speed limit would occur. The new vehicle-matching methodology showed that, after drivers observed a 15-mph drop in the speed limit for cars (10 mph for trucks) on three consecutive VSL signs, they reduced their speed by a median of 7.5 mph (5.8 mph for trucks). Overall, 4% of cars and 10% of trucks complied with the 55-mph speed limit after the observance of three VSL signs.

Cooperative Maneuver Planning for Cooperative Driving

The worthwhile goal of reducing fatalities in road systems inspires people ever since the appearance of the first vehicles. Policy makers, researchers, developers, and others have adopted various measures with a positive effect on the number of fatalities. In Germany, the number dropped from a peak of 21,095 in 1970, to 3,339 in 2013 [1]. Measures include new laws and restrictions by policy makers such as reducing speed limits, penalizing drunken drivers, and enhancing education by driving schools [2]. Researchers and developers mainly focus on technical safety and assistance systems. These systems include the anti-lock braking system (ABS), the electronic stabilization control (ESC), the emergency brake system, adaptive cruise control (ACC), and the lane-keeping control [3].

Modelling the Growing Use of Public Transport in Ile-de-France: How ANTONIN 3 Addresses the Challenge

Ile-de-France, the Paris region, is facing major transport policy challenges. To cope with the previous and forecasted growing use of public transport, restructuration and development of existing lines and achievement of new ones including Grand Paris Express metro are planned. Other transport policy measures are promoted to foster the use of modes alternative to car, such as reduction of roads speed limit or parking policy.In this context, traffic and demand forecasts are required. They rely mostly on the demand model developed and used by STIF, the regional public transport authority. ANTONIN (ANalysis of Transport Organisation and New INfrastructures) is multimodal and based on disaggregate discrete choice models.In continuity with already validated methods in the version ANTONIN 2, the third version which will be operational in 2015 brings innovative solutions and up-to-date functionalities aiming to provide reliable and comprehensive forecasts on the wide range of projects planned in the region. This paper presents the major new features, focussing on what issue they intend to enlighten from the transport authority's perspective, how their effects are taken into account in the model and what tests were made to validate and evaluate them.

Multilevel models to analyze before and after speed data

Analyzing before–after speed data is often limited to a standard comparison of various speed parameters. Although a few studies have used a model-based approach, various limitations exist in terms of both data and methodology. The aim of this paper was to examine the applicability of using multilevel models to analyze before–after speed data and to explore the effect of various temporal, geometrical, and traffic characteristics on traffic speed in an urban residential context. Two multilevel models, one with homogeneous and one with heterogeneous within-site variance, were used for analyzing the hourly free-flow speed data. The study used a dataset collected before and after a posted speed limit (PSL) reduction from 50km/h to 40km/h; the reduction was a pilot program in the city of Edmonton, Alberta, Canada. The results demonstrated the appropriateness of using the multilevel model for analyzing speed data. Moreover, the heterogeneous within-site variance model outperformed the homogeneous counterpart in terms of goodness-of-fit and the precision of parameter estimates. The parameter estimations demonstrated intuitive findings with respect to the effect of various factors on mean free-flow speed. In general, the evaluation results showed that the mean free-flow speed was reduced by 4.6km/h in the after period, when the multilevel model with heterogeneous within-site variances was used. The use of the multilevel model with homogeneous within-site variances slightly underestimated the mean free-flow speed reduction. A separate investigation revealed that the mean free-flow speed was reduced by 5.3km/h and 4.0km/h for local and collector roads, respectively.

Chimpanzees facing a dangerous situation: A high‐traffic asphalted road in the Sebitoli area of Kibale National Park, Uganda

Despite the spread of road infrastructures throughout Africa to support regional development, industry, and tourism, few studies have examined how wild animals adapt their behavior and ecology in road-forest ecotones. Indeed, while numerous studies have demonstrated chimpanzee adaptability in anthropogenic landscapes, none have examined the effects of asphalted highways on wild chimpanzee behaviors. In a 29-month survey, we assessed the dangers posed by an asphalted road crossing the Sebitoli area of Kibale National Park (Uganda). We analyzed 122 individual chimpanzee crossings. Although the asphalted road represents a substantial threat to crossing animals (89 motorized vehicles per hour use this road and individuals of six different primate species were killed in 1 year), chimpanzees took into account this risk. More than 90% of the individuals looked right and left before and while crossing. Chimpanzees crossed in small subgroups (average 2.7 subgroups of 2.1 individuals per crossing event). Whole parties crossed more rapidly when chimpanzees were more numerous in the crossing groups. The individuals most vulnerable to the dangers of road crossing (females with dependents, immature, and severely injured individuals) crossed less frequently compared with non-vulnerable individuals (lone and healthy adolescents and adults). Moreover, healthy adult males, who were the most frequent crossing individuals, led progressions more frequently when crossing the road than when climbing or descending feeding trees. Almost 20% of the individuals that crossed paid attention to conspecifics by checking on them or waiting for them while crossing. These observations are relevant for our understanding of adaptive behavior among chimpanzees in human-impacted habitats. Further investigations are needed to better evaluate the effects of busy roads on adolescent female dispersal and on their use of territories. Mitigation measures (e.g., bridges, underpasses, reduced speed limits, speed-bumps, signposts, or police controls) should be established in this area.

Driver injury severity related to inclement weather at highway–rail grade crossings in the United States

ABSTRACTObjective: Previous studies on crash modeling at highway–rail grade crossings were aimed at exploring the factors that are likely to increase the crash frequencies at highway–rail grade crossings. In recent years, modeling driver's injury severity at highway–rail grade crossings has received interest. Because there were substantial differences among different weather conditions for driver's injury severity, this study attempts to explore the impact of weather influence on driver injury at highway–rail grade crossing.Method: Utilizing the most recent 10 years (2002–2011) of highway–rail grade crossing accident data, this study applied a mixed logit model to explore the determinants of driver injury severity under different weather conditions at highway–rail grade crossing.Results: Analysis results indicate that drivers' injury severity at highway–rail grade crossings is strongly different for different weather conditions. It was found that the factors significantly impacting driver injury severity at highway–rail grade crossings include motor vehicle speed, train speed, driver's age, gender, area type, lighting condition, highway pavement, traffic volume, and time of day.Conclusions: The findings of this study indicate that crashes are more prevalent if vehicle drivers are driving at high speed or the oncoming trains are high speed. Hence, a reduction in speed limit during inclement weather conditions could be particularly effective in moderating injury severity, allowing more reaction time for last-minute maneuvering and braking in moments before impacts. In addition, inclement weather-related crashes were more likely to occur in open areas and highway–rail grade crossings without pavement and lighting. Paved highway–rail grade crossings with installation of lights could be particularly effective in moderating injury severity.

Full Bayesian Mixed-Effect Intervention Model for Before–After Speed Data Analysis

The analysis of before–after speed data to evaluate the effectiveness of safety interventions is often limited to a non-model-based comparison of speed-related indicators. Moreover, modeling of speed data often does not take into account the nested nature of the data. The objective of the study was to quantify the effect of posted speed limit (PSL) reductions in an urban, residential context. The study employed a mixed-effect intervention model, which could address limitations of existing methods. To model mean free-flow speed and the probability of a speed being below or equal to various thresholds, mixed-effect normal regression and binomial logistic regression models were used. Use of a comprehensive, unique, and disaggregated data set enabled not only the before–after evaluation of the PSL reduction but also the exploration of the effects of various temporal, traffic, and road geometry factors on speed. Results demonstrated the appropriateness of using the mixed-effect model for speed data. Parameter estimations showed that nighttimes; weekends; a high proportion of vans, buses, and trucks; evening peak periods; collector roads; and low hourly traffic volumes were all associated with an increase in the mean free-flow speed and a decrease in the probability of speeds being below or equal to various thresholds. Evaluation results showed the mean free-flow speed was reduced by 3.85 km/h in the after period and that speeds below or equal to 50, 60, 70, and 80 km/h increased by 20.0%, 9.2%, 2.8%, and 0.9%, respectively. All improvements were statistically significant; this finding implied that the PSL reduction was effective at influencing vehicle speed.

Motorists' Speed Response to Nonvariable and Variable Work Zone Speed Limits and Other Work Zone Conditions

Transportation professionals view the setting of appropriate regulatory speed limits on public roads, including those under repair or reconstruction, as an important tool in promoting safe and efficient operations. The Ohio Department of Transportation sponsored a study to evaluate its work zone speed zoning processes. Researchers observed motorists' speed choices upstream of and adjacent to several combinations of work zone conditions and factors that were used to justify reduced speed limits in Ohio work zones. Researchers also observed motorists' speed choices upstream of and within pilot variable work zone speed zones. Researchers confirmed that motorists reduced their speed only if they clearly perceived a need to do so. Therefore, whenever possible, the first work zone speed limit sign should be installed within view of a work zone condition. In general, the speed reduction downstream of the first nonvariable and variable work zone speed limit signs ranged from 1 to 6 mph and 3 to 11 mph, respectively. In addition, researchers found that the speed reduction on entering a lane shift, within a lane closure, and on entering a median crossover ranged from 4 to 15 mph. On the basis of previous research and the results of the studies documented in this paper, the research team developed work zone speed zone guidelines for multi-lane highways with original posted speed limits greater than or equal to 55 mph. Researchers also made recommendations for where variable work zone speed zoning should be considered.

Speed limit reduction in urban areas: A before–after study using Bayesian generalized mixed linear models

In fall 2009, a new speed limit of 40km/h was introduced on local streets in Montreal (previous speed limit: 50km/h). This paper proposes a methodology to efficiently estimate the effect of such reduction on speeding behaviors. We employ a full Bayes before–after approach, which overcomes the limitations of the empirical Bayes method. The proposed methodology allows for the analysis of speed data using hourly observations. Therefore, the entire daily profile of speed is considered. Furthermore, it accounts for the entire distribution of speed in contrast to the traditional approach of considering only a point estimate such as 85th percentile speed. Different reference speeds were used to examine variations in the treatment effectiveness in terms of speeding rate and frequency. In addition to comparing rates of vehicles exceeding reference speeds of 40km/h and 50km/h (speeding), we verified how the implemented treatment affected “excessive speeding” behaviors (exceeding 80km/h). To model operating speeds, two Bayesian generalized mixed linear models were utilized. These models have the advantage of addressing the heterogeneity problem in observations and efficiently capturing potential intra-site correlations. A variety of site characteristics, temporal variables, and environmental factors were considered. The analyses indicated that variables such as lane width and night hour had an increasing effect on speeding. Conversely, roadside parking had a decreasing effect on speeding. One-way and lane width had an increasing effect on excessive speeding, whereas evening hour had a decreasing effect. This study concluded that although the treatment was effective with respect to speed references of 40km/h and 50km/h, its effectiveness was not significant with respect to excessive speeding-which carries a great risk to pedestrians and cyclists in urban areas. Therefore, caution must be taken in drawing conclusions about the effectiveness of speed limit reduction. This study also points out the importance of using a comparison group to capture underlying trends caused by unknown factors.

An environmental, economical and socio-political analysis of a variety of urban air-pollution reduction policies for primary PM10 and NOx: The case study of the Province of Milan (Northern Italy)

Abstract In the frame of urban air-pollution reduction policies, economic costs and environmental benefits of a variety of actions have been quantitatively assessed for the Province of Milan (Northern Italy), focusing on PM10 and NOx emission sources. Short-to-mid-term interventions that have been taken into consideration include reduction of inner temperature in residential buildings, banning of residential biomass heating systems, banning of diesel fuelled domestic boilers, night-time streets washing, speed limit reduction on highways, circulation restrictions of oldest EURO vehicles, conversion of diesel buses to natural gas, car sharing/biking promotion, DPF adoption in diesel vehicles, extension of road lanes for urban buses, energy efficiency refurbishment in residential buildings. Re*sults emerged from the cost–benefit analysis integrated with socio-political indicators obtained through direct surveys, will contribute, with an holistic and multidisciplinary approach, to drive the local administrators to implement the most suitable actions in one of the most polluted areas in west-Europe.

Ship strikes threaten blue whale numbers

Marine Biology Whale-ship collisions may be behind low blue whale population counts despite international protections. Irvine et al. used satellites to track 171 blue whales off California over 15 years. The whales, part of the eastern North Pacific population, returned each summer to krill-rich upwelling zones off Santa Barbara and San Francisco—areas also crossed by major shipping lanes. At least three blue whales were killed by ship strike during 2 weeks in 2007. But a similar problem in Canada's Bay of Fundy offers hope: Eleven years ago, its maritime industry moved a shipping lane and reduced speed limits, reducing the likelihood of vessels striking right whales by 80%. ![Figure][1] A blue whale killed by a ship strike PHOTO: FLIP NICKLIN/MINDEN PICTURES PLOS ONE 10.1371/journal.pone.0102959(2014). [1]: pending:yes

Targeting mitigation efforts: The role of speed limit and road edge clearance for deer–vehicle collisions

ABSTRACTDeer–vehicle collisions (DVCs) have major social, economic, and animal welfare costs. Modeling of accident risk relative to environmental characteristics could enable managers to plan the layout of new roads or determine optimal location of mitigation measures to reduce the number of accidents on existing roads. We analyzed position data providing road crossings from 67 global positioning system (GPS)‐marked red deer (Cervus elaphus) and location data of 271 car killed deer within the home ranges of the GPS‐marked red deer. We modeled collision risk as a function of speed limit, season, road characteristics, and habitat features. For a subset of the data, we tested if vegetation clearance along a highway reduced the collision frequency of red deer. The relative risk for DVCs increased with speed limit. We found a higher risk for DVCs during winter compared to the other seasons. Forest cover, distance to pasture, and terrain ruggedness substantially affected risk of DVCs. Road edge clearance reduced the frequency of DVCs, but the effect appeared in the winter season only with a decrease of 53%. Our study highlights that speed limit reduction and road edge clearance are both powerful mitigation tools to reduce the number of DVCs. © 2014 The Wildlife Society.

Re-cycling a city – Examining the growth of cycling in Dublin

In the past few decades much research has been conducted on the increasing numbers of commuters taking up cycling to work. This modal shift has been encouraged by pro-cycling policies to increase the attractiveness of cycling and the construction of new cycling infrastructure. In Dublin, several policies have been applied such as a bike rental scheme, bicycle-purchasing schemes, reducing speed limits and the construction of segregated cycle lanes to promote cycling. This paper seeks to examine what, if any, impact these policies have had on cycling rates in Dublin. This paper compares census data from 2006 and 2011 to determine how cycling rates have changed and if the demographics of cyclists have changed in the city. The results presented in the paper show that cycling rates have increased in Dublin and that a greater percentage of females, those in higher age and socio-economic groups are cycling to work on a regular basis. The analysis presented in this paper identifies groups of individuals that have recently shifted to cycling to work, by identifying who these people are, policymakers can tailor strategies to target these groups to encourage others in these groups to take up cycling.

Assessing the Impact of Speed Limit Changes on Urban Motorways: A Simulation Study in Lille, France

Recent directives in France on sustainable development have driven local Authorities to the reduction of speed limits on urban highways. Consequently, Local Authorities are interested in a thorough evaluation of this measure and in the estimation of the potential impact upon traffic and emissions.In this paper, we undertake an a priori evaluation of speed limit reduction from 110km/h to 90km/h on the Lille motorway network, in France. We first provide an overview of key lessons learned from previous speed limit reduction experiences. Then, we present the methodology of the specific prior evaluation on the Lille network. In particular, we use a first order macroscopic traffic simulation tool for this a priori assessment. The model is first calibrated and then statistically validated using traffic data. This statistical validation is consistent with good practices in simulation. The evaluation output allows for a thorough understanding of the impacts on prevailing traffic conditions and air pollution. Additional scenarios are also considered in order to take into account driver behaviour on the non-compliance with speed limits.Besides the various limitations of the study, especially those related to its predictive aspects, we can conclude that the intended measure will have a positive impact on traffic and emissions. Nevertheless, the magnitude of this impact is largely variable, in particular in regards to driver compliance.

Temporary speed limit changes: An econometric estimation of the effects of the Spanish Energy Efficiency and Saving Plan

Nowadays, speeding is one of the most relevant problems for traffic safety and most resistant to change in motorized countries. The key instruments in Speed Management Policy are speed limits. This road safety strategy is often established or changed, in order to save fuel during periods of rising prices. However, the relationship between speed limits and traffic accidents, is a topic widely discussed by researchers, and there seems to be some consensus about “speed kills.” By applying advanced time series models of unobserved components, our study investigates the impact of a temporary reduction of maximum speed limits, implemented in Spain in 2011, in terms of fuel consumption and fatalities. Our analysis shows that this measure caused a positive effect, although with a limited statistical significance, on fuel consumption and a discrete reduction in road mortality.

How effective are policies to reduce gasoline consumption? Evaluating a set of measures in Spain

Using a panel of 48 provinces for four years we empirically analyze a series of temporary and permanent policies aimed at curbing fuel consumption implemented in Spain between March and June 2011. The first policy was a reduction in the speed limit in highways. The second policy was an increase in the biofuel content of fuels used in the transport sector. The third measure was a decrease of 5% in commuting and regional train fares that resulted in two major metropolitan areas reducing their overall fare for public transit. The results indicate that the speed limit reduction in highways lowered gasoline consumption by 2% to 3%, while an increase in the biofuel content of gasoline increased this consumption. This last result is consistent with experimental evidence that indicates that mileage per liter falls with an increase in the biofuel content in gasolines. As for the reduction in transit fares, we do not find a significant effect for this policy. However, in specifications including the urban transit fare for the major cities in each province the estimated cross-price elasticity of the demand for gasoline – used as a proxy for car use – with respect to the price of transit is within the range reported in the literature. This is important since one of the main efficiency justifications for subsidizing public transit rests on the positive value of this parameter and most of the estimates reported in the literature are quite dated.

Standing in cost-benefit analysis of road safety measures: A case of speed enforcement vs. speed change

Elvik (2006) discussed the appropriateness of including the benefits that offenders get when violating traffic laws. While concluding that these benefits could not be given standing, Elvik resorted to argumentation from normative theories outside the schools of economic theory. In this article, we present arguments for omitting violators' benefits, or lost benefits, based on normative stands within economics school of thought. By means of two examples, we illustrate the distinction between a project of increased/improved enforcement of existing speed limits, where violators' time losses should not be included – compatible with Elvik's point of view – and a project of reduced speed limits, where the time loss should be included. This clarification of standing in cost-benefit analysis of road safety measures is based on the economics school of thought, where cost-benefit analysis is regarded as a decision tool operating within social constraints and where speed limits are considered as absolute institutions.

How Effective are Policies to Reduce Gasoline Consumption? Evaluating a Quasi-Natural Experiment in Spain

Using a panel of 48 provinces for four years we empirically analyze a series of temporary policies aimed at curbing fuel consumption implemented in Spain between March and June 2011. The first policy was a reduction in the speed limit in highways. The second policy was an increase in the biofuel content of fuels used in the transport sector. The third measure was a reduction of 5% in commuting and regional train fares that resulted in two major metropolitan areas reducing their overall fare for public transit. The results indicate that the speed limit reduction in highways reduced gasoline consumption by between 2% and 3%, while an increase in the biofuel content of gasoline increased this consumption. This last result is consistent with experimental evidence that indicates that mileage per liter falls with an increase in the biofuel content in gasolines. As for the reduction in transit fares, we do not find a significant effect for this policy. However, in specifications including the urban transit fare for the major cities in each province the estimated cross-price elasticity of the demand for gasoline - used as a proxy for car use - with respect to the price of transit is within the range reported in the literature. This is important since one of the main efficiency justification for subsidizing public transit rests on the positive value of this parameter and most of the estimates reported in the literature are quite dated.