Changing vehicle and driver population characteristics makes it necessary to periodically reexamine highway design criteria. The speed-change lane is one of the most common highway features because it can be either a permanent feature (terminals, lane drops, etc.) or a temporary feature (construction and maintenance zones).

The objective of this research was to examine the current design parameters which establish speed-change lane length. Based on a review of current practice, updated vehicle performance characteristics, and new driver-behavioral data, recommended design procedures were developed for specific applications taking into account the type of facility, geometrics, and other relevant considerations. This research addressed existing and new acceleration and deceleration lanes on freeways. The scope of this research did not include (a) the design of weaving sections, (b) work zone applications, (c) ramp metering, and (d) new accident studies.

All research has been completed and the project panel has reviewed the final report and user design guidelines. The research agency has completed revising documentation which was provided to the AASHTO Geometric Design Task Force for consideration in revisions to the AASHTO "Green Book." The final report will not be published in the regular NCHRP series, but the contractor's final report is available here.