In an era of multimodal design and expensive right-of-way, transportation agencies must make decisions on how to safely accommodate all users of the roadway system. One of the key decisions that affects roadway operation and safety is the selection of lane widths. Previous research projects have examined the relationship between lane width and safety on urban and suburban arterials. These studies showed inconsistent results on whether or not the use of lane widths narrower than 12 feet on urban and suburban arterials increased crash frequencies. Therefore, there is a need to provide guidelines for state departments of transportation (DOTs) on selecting the appropriate lane widths and understanding the safety impacts of lane width decisions.

The objective of this research was to develop guidelines for the selection of an appropriate lane width considering bike and parking lanes on urban and suburban arterials. The guidelines should incorporate the assessment of safety impacts of lane width in the decision-making process.