The objectives of this research were to formulate a methodology to evaluate potential applications of strategies to increase the capacity of urban freeways by utilising shoulders with or without narrow lanes and to develop recommendations and design guidelines for the implementation of projects involving these strategies. The research focused on the operational and safety performance of various applications of these strategies at 52 sites in 11 corridors throughout the country. Analysis of accident data for five corridors and operational data for all 11 corridors was performed. Accident rates for unaltered and altered corridor segments were developed as well as accident rates for specific sites. Operational data were used to assess impacts on speed-flow relationships and capacity resulting from the use of these strategies. The research confirmed that shoulders and narrow lanes can be effectively used to increase capacity in congested urban corridors. However, findings indicate that in many instances there may be measurable negative impacts to the overall safety performance of the corridor. These strategies should be considered for areas of limited length and having turbulent flow conditions as one alternative for achieving smoother flow. Such use should be typically limited to sections of one mile or less. The report includes a recommended process for evaluating proposed projects and guidelines for implementation of projects. (A)
Samenvatting