Road Diet Research Articles

ROAD DIETS IMPACT ON DRIVING BEHAVIOR AMONG OLDER ADULTS WITH AND WITHOUT PRECLINICAL ALZHEIMER’S PATHOLOGY

Abstract Road diets (that is, the reallocation of one or more lanes of car traffic to other uses) have been proposed as a modification to increase pedestrian safety, particularly for older adults. We considered the impacts of road diets on aging drivers, and on those with early pathological accumulation of AD. We observed naturalistic driving data for 60 cognitively normal older drivers (Age Range = 62 – 87 years, Median = 75 years) driving across three road segments located in St. Louis, Missouri. We used neuroimaging and lumbar puncture derived biomarker data to determine which of the drivers had preclinical AD. Since previous AD studies identified a variety of changes in driving behavior among older drivers with preclinical AD, we examined driving speed before and after lane repurposing. We found that drivers with preclinical AD drove at lower speeds compared to those without preclinical AD prior to road diet implementation. After lanes were repurposed, there was no statistical difference in the speed between older drivers with and without preclinical AD. We evaluated cognitive performance and found that attentional control had a mediating effect on driver speed, suggesting that an individual’s ability to focus on a specific task and filter out distractions was associated with faster driving. Driving speed after lane repurposing is not mediated by attentional control, suggesting that road diets are impervious to individual driver capacity. We conclude that lane repurposing has potential as an important mobility infrastructure solution that could enhance older driver safety and facilitate aging in place.

Take the High (Volume) Road: Analyzing the Safety and Speed Effects of High-Traffic-Volume Road Diets

Cities nationwide have adopted so-called road diets to improve traffic safety, though they are sometimes met with intense opposition from motorists who fear that road diets will increase traffic delays. Road diets typically convert four-lane roadways with no left-turn lanes into streets with a center left-turn lane, two through-traffic lanes, and (often) bicycle lanes and right turn pockets at intersections. The resulting safety improvements are often dramatic. The Federal Highway Administration currently recommends that road diets should be applied to roadways with fewer than 20,000 average daily trips, but that cities should carefully consider whether to apply road diets above 20,000 average daily traffic (ADT). However, study of higher-traffic-volume road diets to inform decisions about them has been limited. In particular, there is scant evidence that safety benefits erode and traffic delays increase meaningfully above this threshold, though this is implied by the 20,000-ADT threshold. To address this literature gap, we examined the safety and traffic outcomes of high-traffic-volume road diets in Los Angeles, CA. To do this, we compared collisions on five high-traffic-volume road diet corridors with 16 similar multilane, untreated street segments. We found that collisions, injuries, and deaths were lower by 31.2% to 100%, depending on the measure, whereas traffic speeds were lower by about 6.7% (peak) to 7.9% (off-peak). We concluded that in Los Angeles higher-traffic-volume road diets appeared to significantly increase safety with only minor effects on traffic speeds.

Differential impacts of road diets on driving behavior among older adults with and without preclinical Alzheimer’s pathology

The driving populace of the United States is aging. The prevalence of Alzheimer disease (AD) will increase in the coming decades. Road diets (that is, the reallocation of one or more lanes of car traffic to other uses) have been proposed as a modification to increase pedestrian safety, particularly for older adults. In contrast, we considered the impacts of road diets on aging drivers, and on those with early pathological accumulation of AD. We observed naturalistic driving data for 60 cognitively normal older drivers (Age Range = 62–87 years, Median = 75 years) driving across three road segments located in the St. Louis metropolitan area, Missouri, United States. We used neuroimaging and lumbar puncture derived biomarker data to determine which of the drivers had preclinical AD. Since previous AD studies identified a variety of changes in driving behavior among older drivers with preclinical AD, we examined driving speed before and after lane repurposing. We found that drivers with preclinical AD drove at lower speeds compared to those without preclinical AD prior to road diet implementation. After lanes were repurposed, there was no statistical difference in the speed between older drivers with and without preclinical AD. We evaluated cognitive performance and found that attentional control had a mediating effect on driver speed, suggesting that an individual’s ability to focus on a specific task and filter out distractions was associated with faster driving. Driving speed after lane repurposing is not mediated by attentional control, suggesting that road diets are impervious to individual driver capacity. We conclude that lane repurposing has potential as an important mobility infrastructure solution that could enhance older driver safety and facilitate aging in place.

An exploration of multiuser perceptions of a Norwegian Complete Streets modification using interim design strategies

The need for cities worldwide to embrace sustainable transportation alternatives has given rise to innovative planning and design practices such as the use of Complete Streets. This research article presents an approach that utilizes interim design strategies to investigate users’ perceptions of Complete Streets modifications and their impact on travel behavior. The study focused on a major street in Trondheim, Norway, where various low-cost interim street changes were implemented to enhance conditions for pedestrians, cyclists, and transit users. These changes involved measures such as a ban on through-driving, a road diet (lane reduction initiative), bicycle lanes with armadillo separators, the deactivation of traffic lights, and parklet installation. Multiuser perceptions of the modifications were explored with the help of 832 online ex-post survey responses from city center residents and street users. Additionally, manual before-and-after counts of cyclists were conducted on the target street and three parallel streets. The findings revealed that employing interim design strategies enables transport planners to gain practical insights into the effectiveness of different Complete Streets measures. This, in turn, facilitates the optimization of roads for diverse travel modes and user needs.

Evaluating the Feasibility of Road Diets for Advancing Urban Mobility in Newark, DE

Evaluating the Feasibility of Road Diets for Advancing Urban Mobility in Newark, DE

A Comprehensive Study of a Road Diet Implementation in the US and Abroad

A Comprehensive Study of a Road Diet Implementation in the US and Abroad

Measuring congestion at road-diet reductions using probe vehicle data

Road diets provide a means to reduce traffic speeds and promote alternative travel modes within the United States. Throughout the state of New Jersey there are approximately 50 existing road diets with more planned. While research has shown that road diets improve safety, no defined means to measure their long-term impact on traffic flow were found. This paper explores some new and existing means for applying intelligent transportation techniques to quantify long-term congestion changes through commercial anonymous probe vehicle (APV) speed data, the annual average daily traffic and other factors. Two case studies are used to evaluate congestion performance metrics, analysing 8 million APV speed records. Although there are a number of variables to consider, this preliminary research establishes a base measure for evaluating the pre- and post-road-diet impact on traffic flow.

Walkability and importance assessment of pedestrian facilities on central business district in capital city of Indonesia

The City of Jakarta has changed the paradigm of transportation development policy in order to prioritize pedestrians. This research aims to examine the walkability of Sudirman-Thamrin central business district. The research used the modified Global Walkability Index (GWI) method. This method was used because the parameters have been adjusted to the characteristics of pedestrians in big cities in Asia. The findings of this research show that revitalization of sidewalk using the road diet concept can increase walkability up to 38.98%. It also has an impact on increasing the number of public transportation users by 15.41%.The Sudirman–Thamrin area, as a pilot project location for sidewalk revitalization, can be used as an example to be applied in other locations. The findings of this research for international readers can be used as lessons on how an area that was previously a car oriented city has turned into an area that prioritizes pedestrians which also has implications for increasing the value of walkability and public transportation users. Furthermore, the walkability parameters were grouped into four aspects to find out the correlation between walkability and the four aspects. In previous GWI research, the analysis of this correlation was not conducted. According to the IPA results, four parameters were considered important and high performance. In addition, the results of the correlation test analysis showed that the accessibility and supporting facilities were considered having a strong relationship with walkability. On contrary, safety aspect and convenience aspect were considered having a low relationship with walkability.

Mixed-methods approach to studying multiuser perceptions of an interim Complete Streets project in Norway

Research on multiuser perceptions of street environment alterations has been gathering attention in recent years given an increased focus on both sustainable city development and public participation. This study investigated the value of applying a mixed-methods approach to investigating user perceptions of Complete Streets projects. It employed an online survey of 719 users of a case study street in Trondheim, Norway which received an interim infrastructural treatment including a road diet and a separated bicycle path. The survey presented the respondents with manipulated photographs showing the implemented interim design solution and six different potential streetscape configurations in order to explore their street design preferences. Additionally, the use of an integrated mapping application programming interface (API) allowed the participants to place markers with comments along the project map to explain where and why they had felt unsafe in relation to their use of the street before and after the implementation of the interim street modification, although both were collected in the after period. The ability of users’ demographic characteristics and transport behavior to explain variations in perceptions and preferences was explored. It was confirmed that the participants favored separated bicycle path designs and that their preferences did not vary considerably among the different user types. The analysis of the distribution of the unsafe points from both time periods helped in the identification of traffic safety issues that might not have been uncovered if only stated preference methodologies were used. Additionally, it was shown that implementing such street alternations as interim projects could be beneficial for the planning process by providing the planners with insights on the way changes to the street environment would be experienced by the users.

Safety Effectiveness of the Road Diet Treatment in Rhode Island

A road diet is a low-cost countermeasure which typically involves converting an existing four-lane undivided roadway to a three-lane roadway, reducing the section to two through lanes and a center two-way left-turn lane. The objective of this evaluation was to estimate the safety effectiveness of road diets by developing a crash modification factor (CMF) specific to the U.S. state of Rhode Island. To account for potential selection bias and regression-to-the-mean, an empirical Bayes before-after analysis was conducted, using reference groups of untreated four-lane undivided roadways with similar characteristics to the treated sites. Results indicated a 29% decrease (CMF = 0.71) in total crashes and a 37% reduction in fatal and injury crashes (CMF = 0.63). The expected results of the evaluation will help Rhode Island Department of Transportation to determine a statewide direction for implementation of the countermeasure.

Development of Road Diet Segment and Intersection Crash Modification Factors

Road diets can offer potential safety improvements for both pedestrians and vehicles. The additional space provided by reducing the number of vehicular through lanes can be reallocated to other uses such as bicycle lanes, parking, sidewalks, transit use, turn lanes, curb extensions, parklets, or pedestrian refuge islands. This study evaluated the safety effectiveness of road diets in Virginia using the empirical Bayes method, focusing on the common road diet conversion from a four-lane roadway to a three-lane roadway with added bike lanes. A total of 36 segment sites and 39 intersections were identified in Virginia where road diet installations were implemented between the years 2009 to 2018. The analysis showed segment crash modification factors (CMFs) of 0.62 for total crashes and 0.36 for fatal and injury (FI) crashes. Across all intersection types, the CMFs were 0.65 for total crashes and 0.54 for FI crashes. All CMFs were found to be statistically significant at a 95% confidence level. When intersections were separated into signalized and unsignalized intersections, no significant safety benefit was found for unsignalized intersections. Based on the results, it was concluded that road diets can potentially reduce crashes, and public agencies should consider the safety benefits of road diets when justifying roadway improvements.

Nighttime pedestrian fatalities: A comprehensive examination of infrastructure, user, vehicle, and situational factors

Introduction: Pedestrian fatalities in the United States increased 45.5% between 2009 and 2017. More than 85% of those additional pedestrian fatalities occurred at night. Method: We examine Fatality Analysis Reporting System (FARS) data for fatal pedestrian crashes that occurred in the dark between 2002 and 2017. Within-variable and before/after examinations of crashes in terms of infrastructure, user, vehicle, and situational characteristics are performed with one-way analysis of variance (ANOVA) and two-sample t-tests. We model changes in crash characteristic proportions between 2002–2009 and 2010–2017 using linear regressions and test for autocorrelation with Breusch-Godfrey tests. Results: The increase in fatal nighttime pedestrian crashes is most strongly correlated with infrastructure factors: non-intersection unmarked locations (saw 80.8% of additional fatalities); 40–45 mph roads (54.6%); five-lane roads (40.7%); urban (99.7%); and arterials (81.1%). In addition, SUVs were involved in 39.7% of additional fatalities, overrepresenting their share of the fleet. Increased pedestrian alcohol and drug involvement warrant further investigation. The age of pedestrians killed increased more (18.1%) than the national average (3.2%). Conclusions: By identifying factors related to the increase in nighttime pedestrian fatalities, this work constitutes a vital first step in making our streets safer for pedestrians. Practical Applications: More research is needed to understand the efficacy of different solutions, but this paper provides guidance for such future research. Engineering solutions such as road diets or traffic calming may be used to improve identified infrastructure issues by reducing vehicle speeds and road widths. Rethinking vehicle design, especially high front profiles, may improve vehicle issues. However, the problems giving rise to these pedestrian fatalities are likely a result of not only engineering issues but also interrelated social and political factors. Solutions may be correspondingly comprehensive, employing non-linear, systems-based approaches such as Safe Systems.

Evaluation of the Use of a Road Diet Design: An Urban Corridor Case Study in Washington, DC

A traditional road diet design converts a four-lane two-way road to a three-lane road consisting of two through lanes and a center two-way left turn lane. This paper introduces a new application of the road diet design in an urban corridor. Specifically, the new application converts a four-lane two-way road into a two-lane two-way road with full-time parking lanes in both directions. The paper analyzed the traffic impacts of the road diet application on the corridor of New Jersey Avenue, northwest, in the city of Washington, District of Columbia. The corridor included five signalized and one unsignalized intersections. Before-and-after analyses using Synchro 11 simulation and Site-Specific Empirical Bayes analysis were used to evaluate and compare existing and proposed scenarios. The proposed scenario provided various benefits including offering accessibility to the businesses in the area and acting as a traffic calming strategy. For signalized intersections, the overall performance remained the same for most intersections except for one intersection (on P Street), as it is significantly impacted by the road diet design due to the dramatic increase of traffic volumes in its minor streets as a result of diverting traffic volumes from the unsignalized intersection for left and through movements. Results showed that the use of a road diet design enhanced the unsignalized intersection performance due to the traffic volume divergence from its minor streets and enhanced the safety of the study area by decreasing the annual number of predicted crashes. To achieve better operational benefits and reflect traffic demands, the paper recommends to re-optimize signal timings when a road diet design is adopted.

Microscopic Traffic Simulation as a Decision Support System for Road Diet and Tactical Urbanism Strategies

Urban street networks in the United States have been primarily designed for automobile traffic with negligible considerations to non-motorized transportation users. Due to environmental issues and quality of life concerns, communities are reclaiming street spaces for active modes and slowing the speeds in their downtown. Moreover, tactical urbanism, i.e., the use of street space for innovative purposes other than moving automobile traffic, is becoming attractive due to reduced automobile travel demand and the need for outdoor activities in the age of the COVID-19 pandemic. This study provides details of the modeling of an urban downtown network (in the City of San Jose) using microscopic traffic simulation. The model is then applied to evaluate the effectiveness of street design changes at varying demand scenarios. The microsimulation approach was chosen because it allows for the detailed modeling and visualization of the transportation networks, including movements of individual vehicles, bicyclists, and pedestrians. The street design change demonstrated here involves one-way to two-way street conversion, but the framework of network-wide impact evaluation may also be used for complete street conversions. The base conditions network was also tested under different travel demand reduction scenarios (10%, 20%, and 30%) to identify the corridors in the city network in which the tactical urbanism strategies (e.g., open-air dining) may be best accommodated. The study provides framework for the use of a microscopic model as part of a decision support system to evaluate and effectively implement complete streets/tactical urbanism strategies.

Influence of road lane reductions on motorised and non-motorised traffic safety

Road lane reduction with the addition of roadway countermeasures (also known as a ‘road diet’) is a transportation planning treatment to achieve systemic traffic improvements. Although lane reductions are expected to increase traffic safety overall, the impacts may vary by different roadway characteristics among sites and by crash types. The main objective of the study reported in this paper was to identify the effectiveness of lane reductions considering various factors including roadway characteristics through estimating crash modification factors (CMFs) for different crash types. The study first evaluated the CMFs for lane-reduction cases to check the overall safety effects using the observational before and after comparison group method. Second, the variation of CMFs due to different roadway characteristic factors was identified. Ultimately, the CMFs were developed for different crash types and severities. The results of the estimated CMFs indicated that lane reductions decreased crash frequency in general. From the CMFs with different traffic volume ranges, it was found that lane reductions have higher safety impacts to reduce total and injury crashes when there are fewer vehicles on roadways.

Evaluation of Lane Reduction “Road Diet” Measures in China

Road diet measures are widely used abroad, but they have not been implemented in China. One of the important reasons is that we usually think that the reduction of the number of lanes will cause traffic congestion. In order to evaluate the impact of lane reduction “road diet”measures, we implemented road diet reform measures in Shoushan Road to Longxing Road section of Xinghai North Street, Xingcheng City. After nearly one year of adaptation, we evaluate the implementation plan from three aspects in this study: safety, operation, and subjective feeling. Then design a questionnaire to investigate the subjective feelings of drivers, bicyclists and pedestrians on road diet measures. The questionnaire data shows that 56% of drivers has been illegally occupying the non-motorized road or central yellow line area, the main reason is that the speed of the vehicle ahead is too slow and there is no illegal capture equipment. More than 70% of bicyclists believe that their number of rides has increased. More than 90% of pedestrians think it is easier to cross the street, and they used to stay in the central yellow line area. Using VISSIM and SSAM to evaluate the traffic operation and safety aspects before and after the road reform, the results show that after the reform, the average speed decreases by about 5km/h, the travel time for left turn on the road segment generally increases, and the number of conflict points decreases by about 33%.

The Importance of Urban Transportation, Managements and Strategies for Sustainable City

In urban planning, the need for sustainable solutions is increasing day by day to facilitate and improve human life. With the developing technology, cities are tried to be transformed into sustainable cities by using smart city technologies. This article is about current problems in urban transportation planning and new developments. It is also an introduction to the subject. Papers on this issue emphasize how physical mobility is still an important priority for urban life. Five features have been identified regarding emerging urban transport, management and strategies. The first descriptive feature, the relationship between land use and transportation. The second is sustainable urban mobility, which estimates future generations and resources to improve the quality of life in cities by prioritizing physical and biological health. The third feature is the concept of accessibility and mobility in urban and pedestrian. The fourth feature is the concept of “road diet” that managers use persistently but do not succeed in. Urban transport planning is a communication-oriented activity and new transport services in relation to other professions and policy sectors. The cities, which are exemplified numerically and visually, have been selected among the cities which may be examples to the other developing cities of the world.

Evaluation of the Effectiveness on the Implementation of a Two-Way Left-Turn Lane with Educational Material in Highway PR-107 using a Driving Simulator

The road diet concept has been implemented around the United States for more than three decades. Road diets are at the early stages of implementation in Puerto Rico and the use of a Two-Way Left Turn Lane (TWLTL) will be a new and unfamiliar design for local drivers. For this reason, the effectiveness of a TWLTL was evaluated using a driving simulator with local drivers for a segment of highway PR-107 in Puerto Rico. This highway is a suburban commercial corridor without access control that had a 67% increase in crashes between 2015 and 2016. This highway was selected because of its large number of left-turn maneuvers and more than 40% of the total crashes were rear-end type crashes. The University of Puerto Rico at Mayaguez Driving Simulator was used to evaluate drivers’ performance by observing vehicle speeds and positions along two simulated road scenarios: 1) the existing cross-section and 2) a modified cross-section with a TWLTL. Subjects were divided into two groups: 1) subjects who received training about the correct operation on a TWLTL before the simulation runs and 2) subjects who did not receive any prior training. The results indicate a positive effect of the educational material on driver behavior. Subjects who received training about the TWLTL showed a 66% increase in maneuver improvement, less variability in the position at which they entered the TWLTL, and lower variance of the mean speed than those who did not receive TWLTL training before driving through the simulation.

Making intersections safer with I2V communication

Intersections are hazardous places. Threats arise from interactions among pedestrians, bicycles and vehicles, more complicated vehicle trajectories in the absence of lane markings, phases that prevent determining who has the right of way, invisible vehicle approaches, vehicle obstructions, and illegal movements. These challenges are not fully addressed by the “road diet” and road redesign prescribed in Vision Zero plans, nor will they be completely overcome by autonomous vehicles with their many sensors and tireless attention to surroundings. Accidents can also occur because drivers, cyclists and pedestrians do not have the information they need to avoid wrong decisions. In these cases, the missing information can be computed and broadcast by an intelligent intersection. The information gives the current full signal phase, an estimate of the time when the phase will change, and the occupancy of the blind spots of the driver or autonomous vehicle. The paper develops a design of the intelligent intersection, motivated by the analysis of an accident at an intersection in Tempe, AZ, between an automated Uber Volvo and a manual Honda CRV and culminates in a proposal for an intelligent intersection infrastructure. The intelligent intersection also serves as a software-enabled version of the ‘protected intersection’ design to improve the passage of cyclists and pedestrians through an intersection.

An examination of the increases in pedestrian motor-vehicle crash fatalities during 2009–2016

IntroductionPedestrian fatalities increased 46% in the United States during 2009–2016. This study identified circumstances under which the largest increases in deaths occurred during this period. MethodAnnual counts of U.S. pedestrian fatalities and crash involvements were extracted from the Fatality Analysis Reporting System and General Estimates System. Poisson regression examined if pedestrian fatalities by various roadway, environmental, personal, and vehicle factors changed significantly during 2009–2016. Linear regression examined changes over the study period in pedestrian deaths per 100 crash involvements and in horsepower per 1000 pounds of weight among passenger vehicles involved in fatal single-vehicle pedestrian crashes ResultsPedestrian deaths per 100 crash involvements increased 29% from 2010, when they reached their lowest point, to 2015, the most recent year for which crash involvement data were available. The largest increases in pedestrian deaths during 2009–2016 occurred in urban areas (54% increase from 2009 to 2016), on arterials (67% increase), at nonintersections (50% increase), and in dark conditions (56% increase). The rise in the number of SUVs involved in fatal single-vehicle pedestrian crashes (82% increase) was larger than the increases in the number of cars, vans, pickups, or medium/heavy trucks involved in these crashes. The power of passenger vehicles involved in fatal single-vehicle pedestrian crashes increased over the study period, with larger increases in vehicle power among more powerful vehicles. ConclusionsEfforts to turn back the recent increase in pedestrian fatalities should focus on the conditions where the rise has been the greatest. Practical applicationsTransportation agencies can improve urban arterials by investing in proven countermeasures, such as road diets, median crossing islands, pedestrian hybrid beacons, and automated speed enforcement. Better road lighting and vehicle headlights could improve pedestrian visibility at night.