More on Trucks and Turning

For more about what works and what doesn't work in roadway design, here are two references

California Dept of Transportation Highway Design Manual

National Cooperative Highway Research Program Review of Truck Characteristics as Factors in Roadway Design

This template shows the space needed for a truck to turn. The lines on the template delineate the path of the wheels and the body of the vehicle as the truck moves through the turn. These lines must clear any “obstacles” including curbs, islands, adjacent lanes, sign structures, traffic delineators, traffic signal and lighting poles, guardrails, trees and rock outcrops. The radius of the template is measured to the outside front wheel path through the curve. The 60-foot radius template is more conservative and is preferred. The 60-foot radius template requires less right of way on the inside of the curve, and it leaves a margin of error for the truck driver. The 60-foot radius template should be used for conditions where the vehicle may not be required to stop before entering the intersection.

When this template is put on a map of the Cambridge/Windom intersection, it is obvious that a truck could never make the right turn from Cambridge Street onto Windom without hitting the median strip and moving into traffic heading south on Windom.