Evolution of Interchange Design in North America

There has been a significant evolution in interchange forms and interchange geometric design
criteria since the first interchange (cloverleaf) was constructed in Woodbridge, NJ in 1928. The
first cloverleaf interchange in Canada was the Port Credit interchange completed in 1937 on the
QEW between Toronto and Niagara Falls which was the first freeway in Canada. This
presentation will chronicle the following:

• Evolution of interchange forms from the cloverleaf to the double crossover diamond (diverging diamond).
• Evolution of interchange geometric design criteria from the 1930’s to the present.
• Application of driver characteristics and expectations in interchange design, operations and signing guidelines in the Transportation Association of Canada (TAC) and the American Association of State Highway and Transportation Officials (AASHTO) design policies and the Manual on Uniform Traffic Control Devices (MUTCD).

The interchange forms to be presented include 17 diamond interchange forms, 10 partial
cloverleaf forms and 16 system (freeway to freeway) interchange forms with their design and
operational characteristics. The early interchanges (1928-1955) in the US and Canada will
provide the base from which the multitude of interchanges have evolved.

Geometric design of ramp exit and entrance design, geometric design of ramps, and basic
design criteria for freeways will be presented demonstrating the evolution of design criteria
from the 1940’s to present day based on TAC and AASHTO criteria.

Application of the research associated with driver characteristics and expectations on freeways
and interchanges and the resultant development of design criteria will be presented. Most of
these guidelines were developed by Jack E. Leisch, who taught at the University of Waterloo
and was VP and Chief Engineer for De Leuw Cather of Canada in the 1960’s.