2013 Session: 672

• Operational and Safety Effects of Using Left-Turn Lanes with Substandard Lengths at Unsignalized Median Openings: Case Study in Houston, Texas
  Abstract: For median-divided roadways, the AASHTO Greenbook specifically encourages the use of left-turn lanes at median openings to eliminate stopping in through-traffic lanes. However, in urban areas, the Greenbook requirements for the lengths of median turn lanes often exceed the available length between two adjacent openings. Thus, left-turn lanes with substandard lengths have been in wide use at median openings on urban arterial roads. The objective of this study was to investigate whether it is operationally effective and safe to use median left-turn lanes of substandard lengths at unsignalized median openings. For this purpose, an analytical model was developed to estimate the delay incurred by left-turn vehicles as they decelerate in through-traffic lanes in preparation for the left-turn maneuvers. A case study was conducted on a 3,000-ft corridor on Jones Rd. in Houston, Texas, where eight median left-turn lanes have been installed, all with substandard lengths. Using calibrated micro-simulation models as benchmarks, the proposed model showed reasonable performance. Actual rear-end crashes and simulated rear-end conflicts generally revealed that such lanes did not result in compromised safety performance.
  Authors: Chen, Xiaoming; Qi, Yi; Liu, Guanqi; Wu, Jianing
  Authors: Chen, Xiaoming; Qi, Yi; Liu, Guanqi; Wu, Jianing
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management; Deploying Transportation Research-Doing Things Smarter, Better, Faster
  Session: 672
  Paper Number: 13-0071
• Safety Effects of Access Points near Signalized Intersections
  Abstract: According to the National Highway Traffic Safety Administration (NHTSA), every year over five million collisions occur in the US. More than half of these collisions are intersection and access point-related. The main objective of this research was therefore to develop a valid statistical model to estimate the number of access point-related collisions occurring at access points near signalized intersections.Geometric, traffic, and point-related collision data over 5 years, from January 2005 to December 2009 were collected for 108 sites. The average annual daily traffic (AADT) and 14 more independent variables were introduced into the model one by one in a multiplicative form. The final model was selected based on NLMIXED, a nonlinear optimization method, in SAS® to estimate the model parameters and the -2 Log Likelihood and Bayesian information criterion (BIC) statistical criteria. Finally cumulative residual (CURE) plots were used to check the goodness of fit of each model.Out of the 15 independent variables tested, only AADT, driveway width, and through movement queue at the intersection near the access point were statistically significant in developing the collision prediction statistical model. This model could be used by state DOTs and municipal traffic engineers to address access management requirements and to predict problems likely to result from site traffic impacts.
  Authors: Jafari, Reza; Hummer, Joseph E.
  Authors: Jafari, Reza; Hummer, Joseph E.
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management; Deploying Transportation Research-Doing Things Smarter, Better, Faster
  Session: 672
  Paper Number: 13-1218
• Safety Analysis of Suburban Arterials in Shanghai, China
  Abstract: As urban sprawl continues to accelerate in China, more lands are developed along suburban arterials and more people use these roads to commute. This necessarily results in an increase of access points appearing along the suburban arterials, which lead to a raise of traffic safety hazardous. This safety problem requires in-depth analysis to better understand the relationship between roadway design, traffic operation and traffic safety. This study examined a total of 161 roadway segments (each between two adjacent signalized intersections) on eight different suburban arterials in Shanghai. Geometric design features, access point information, and traffic flow characteristics for chosen 161 segments were collected. A preliminary inspection of the data revealed that roadway segments from the same arterials share similar geometry, access and traffic flow characteristics. To account for the spatial correlation, Bayesian Hierarchical models were developed to identify the safety factors at both arterial and segment levels. Three hierarchical Negative Binomial (HNB) models were developed for slight crashes, severe crashes and total crashes. Model comparisons between HNB models and Negative Binomial models have affirmed the existence of spatial correlation. Results showed that the density of signal spacing along arterial (DOSP) on arterials has a significant influence on the three types of crashes frequencies. The non-uniform signal spacing has a significant impact on of the occurrence of slight crashes. At the segment-level, higher frequencies of slight crashes, severe crashes and total crashes tend to occur for the segments in inner suburban areas with curves, the segments with a higher density of access points, and the segments with higher percentage of large-size vehicles. The safety impacts of different variables of traffic composite were also studied.
  Authors: Wang, Xuesong; Song, Yang; Huang, Helai
  Authors: Wang, Xuesong; Song, Yang; Huang, Helai
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management; Deploying Transportation Research-Doing Things Smarter, Better, Faster
  Session: 672
  Paper Number: 13-1727
• Overview of the Draft Roadway Access Management Guidelines for Port Authority of New York and New Jersey
  Abstract: This paper provides an overview of the efforts by the Port Authority of New York and New Jersey (“the Port Authority”) to develop and implement a Roadway Access Management Guidelines document for its airports and ports. The paper first summarizes the process used, including extensive intra-agency coordination, to develop and refine roadway access management guidelines that were tailored for Port Authority facilities. The paper then provides an overview of the draft guidelines that were recommended for each of the primary guidance areas (e.g., traffic signal spacing, unsignalized driveway spacing, etc.). In many cases, the guidelines formalize the practices already used so that access management may be applied more consistently. The draft Guidelines document is currently under review by leadership in the Port Authority’s Engineering/Architecture Design Division with a primary focus on the administrative aspects, such as the variance procedure and language related to intra-agency coordination. The Guidelines document includes an access classification system with associated design criteria tailored to the specific functions of the agency’s roadway facilities.
  Authors: Ginder, Alan; Rivera, Jose M.; Baig, Mirza Rizwan; Lepore, Armando; Gluck, Jerome Steven; Lorenz, Matthew R.
  Authors: Ginder, Alan; Rivera, Jose M.; Baig, Mirza Rizwan; Lepore, Armando; Gluck, Jerome Steven; Lorenz, Matthew R.
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management; Deploying Transportation Research-Doing Things Smarter, Better, Faster
  Session: 672
  Paper Number: 13-4206
• Safety Evaluation of Access Management Policies and Techniques
  Abstract: Access management is the process that provides (or manages) access to land development while simultaneously preserving the flow of traffic on the surrounding road network in terms of safety, capacity, and speed. These benefits have been increasingly recognized at all levels of government and a growing number of agencies are managing access by requiring driveway permit applications and establishing where new access should be allowed. They are also closing, consolidating, or improving driveways, median openings, and intersections as part of their access management implementation strategy. However, these decisions are often challenged for various reasons and there have been few scientifically rigorous evaluations to quantify the safety effects. Therefore, there is a need to provide additional information to help rationalize decisions related to access management so that agencies can better explain the safety benefits of their policies and practices. This study seeks to fill some of the safety-related research gaps, namely to quantify the safety impacts of access management decisions. More than 600 miles of detailed data were collected for corridors representing four regions of the U.S. Crash, roadway, and traffic volume data were collected for each corridor along with specific access management characteristics. Corridors were segmented based on area type and land use, and crash prediction models were estimated using generalized linear modeling. The models, which are presented and illustrated in this paper, provide an opportunity to evaluate the potential safety effects of access management strategies at the corridor level.
  Authors: Gross, Frank; Lyon, Craig; Persaud, Bhagwant; Gluck, Jerome Steven
  Authors: Gross, Frank; Lyon, Craig; Persaud, Bhagwant; Gluck, Jerome Steven
  Year: 2013
  Document Type: Paper
  Subject: Operations and Traffic Management; Deploying Transportation Research-Doing Things Smarter, Better, Faster
  Session: 672
  Paper Number: 13-3921
• Operational and Safety Effects of Using Left-Turn Lanes with Substandard Lengths at Unsignalized Median Openings: Case Study in Houston, Texas
  Authors: Chen, Xiaoming
  Authors: Chen, Xiaoming
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management; Deploying Transportation Research-Doing Things Smarter, Better, Faster
  Session: 672
  Paper Number: 13-0071
• Safety Analysis of Suburban Arterials in Shanghai, China
  Authors: Wang, Xuesong
  Authors: Wang, Xuesong
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management; Deploying Transportation Research-Doing Things Smarter, Better, Faster
  Session: 672
  Paper Number: 13-1727
• Safety Effects of Access Points near Signalized Intersections
  Authors: Jafari, Reza
  Authors: Jafari, Reza
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management; Deploying Transportation Research-Doing Things Smarter, Better, Faster
  Session: 672
  Paper Number: 13-1218
• Overview of the Draft Roadway Access Management Guidelines for Port Authority of New York and New Jersey
  Authors: Ginder, Alan
  Authors: Ginder, Alan
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management; Deploying Transportation Research-Doing Things Smarter, Better, Faster
  Session: 672
  Paper Number: 13-4206
• Safety Evaluation of Access Management Policies and Techniques
  Authors: Gross, Frank
  Authors: Gross, Frank
  Year: 2013
  Document Type: Presentation
  Subject: Operations and Traffic Management; Deploying Transportation Research-Doing Things Smarter, Better, Faster
  Session: 672
  Paper Number: 13-3921