Calculate the additional road width needed on horizontal curves to accommodate vehicle tracking.
This is a simplified approximation based on TAC Geometric Design Guide principles. Final designs should always be verified against the full design tables.
A WB-12 semi-trailer (12.2m wheelbase) on a 50m radius curve, 2 lanes:
Use this for preliminary estimates of road widening on tight horizontal curves, particularly for intersections, roundabouts, or industrial access roads where larger vehicles need to track through.
Final road design must reference the full TAC or AASHTO geometric design tables and account for superelevation, sight lines, and other factors this simplified calculator does not capture.
Use the largest vehicle that will regularly use the road. Residential streets typically use SU trucks, while industrial or highway routes may need WB-15 or WB-20 semi-trailers.
Generally above 200-250m radius, widening requirements become minimal for most design vehicles. Below 100m, widening becomes increasingly significant.