Pedestrian Safety Guide and Countermeasure Selection System
N 130th Street, Seattle, Washington before road diet. Pedestrians had to cross a four-lane roadway.
A traffic analysis should be conducted to determine whether a lane reduction is feasible, (i.e. vehicle capacity exceeds existing and projected volumes; many roadways were built without such analysis and in other cases traffic volumes have receded over time). The most common road diet configuration involves converting a four lane road to three lanes, with one travel lane in each direction and a center two-way left-turn lane (TWLTL), often supplemented with painted, textured, or raised center islands. Left-turning drivers can exit the traffic stream and wait in the TWLTL, while through traffic can maintain a fairly constant speed. Four to three lane conversions should be considered for roadways with documented safety concerns, moderate volumes (less than 15,000 ADT, up to 25,000 ADT in special cases), and along priority bicycle and walking routes.
There are many opportunities to perform road diets, particularly on roadways with wider cross sections, one-way streets (which may have excess capacity), and although not as common, where volumes are low a three lane road (one lane in each direction with a TWLTL) can be converted to two.
Extra roadway space can be reallocated for other roadway users to improve safety, comfort, and convenience (see list above). Reconstruction projects may allow for curb lines to be moved to narrow the roadway. With the additional space created from restriping or reconstruction, space can be redistributed for the following uses:
• Bicycle lanes or cycle tracks, parking lanes, or transit lanes
• Widened sidewalks, landscaped buffers with street trees, and curb extensions at crossings where on-street parking is present
Authors and Acknowledgements