Research to Better Inform the Safety Performance of Local and Urban Roads Related to Design Alternatives and CSS
Context Sensitive Solutions
Community & Cultural Concerns, Environmental Process
Research Idea Scope
TRB 86th Annual Meeting Presentation; The Safety Effects of Urban Principle Arterial Streetscape Redevelopment Projects Including Street Trees: A Context-Sensitive Case Study (2007)
This report documents safety performance of landscaped medians and other streetscape improvements on State Route (SR) 99 in Washington State. Findings contained in this report are based on a before-and-after study of streetscape improvements made in SeaTac, Washington. Findings from the first two phases of SeaTac’s redevelopment project analyses are shown and indicate no significant change in frequency or severity of crashes. Crashes in the combined study area decreased slightly, while SeaTac Phase 2 showed a slight increase. A shift in crash locations occurred, with fewer mid-block and increased intersection crashes. U-turn crashes increased after construction, from four to 35 within three years. These changes relate directly to the access control effects of the medians The number of crashes reporting striking a fixed-object decreased in the Phase 1 roadway segment but increased in the Phase 2 segment. When trees were involved, the small size of the trees appears to have limited the severity of the resulting crash, increasing the likelihood that they would be classified as “property damage only.” Concern related to the future growth of trees and the corresponding increased severity is identified. The findings also shows that placing trees in narrow medians and near road segments with turning movements resulted in high levels of tree strikes.
Urgency and Payoff
Documenting the relationship between local road with (e.g. subdivision roads) and public safety will help justify smart growth techniques that will benefit the environment, and will also save both developers and the taxpayer considerable costs associated with road construction, maintenance, and the deployment of public services and utilities.