The changes are based on a VDOT traffic engineering study.
In the Roanoke area, the change will affect 14.7 miles from about 1 mile south of Exit 137 to about one mile north of Exit 150. In Harrisonburg, it will affect 6 miles from about a mile south of Exit 243 to about 1.5 miles north of Exit 247.
The 40-year-old interstate handles as much as double the amount of traffic it was intended to carry and up to 10 times the volume of trucks. A $3.4 billion project is scheduled that will widen the highway from four lanes to six. Already, rumble strips and stronger guardrails have been installed to improve safety on the interstate.
The two sections in the Roanoke and Harrisonburg areas carry a large number of trucks and many local vehicles that use the interstate as bypasses entering and exiting at intersections spaced closely together, creating a congested situation.
The Virginia Trucking Assn. says it supports the new limits.