Planning of an Unconventional Urban Arterial Intersection A Context Sensitive Design Approach

Calgary’s population has recently exceeded the one million mark. Blessed with an oilrich economy, the City has been experiencing an unprecedented growth, which has created significant additional demands on the municipality’s transportation system. As a result, many of the City’s intersections are now at capacity, and desperately need improvement. Although grade separation solutions for urban arterials are not common because of their higher construction costs and right-of-way (R.O.W.) requirements, the projection of high future traffic volumes on many of Calgary’s urban thoroughfares has forced transportation engineers to examine the use of innovative and unconventional alternatives. Major arterials in built-up urban areas face problems not necessarily present in typical freeway-type interchange design. In such built-up areas, there is usually insufficient room for the construction of expansive loop ramps. Maintaining the existing flow of traffic during implementation is another critical consideration. The proximity of existing commuter transit and/or freight rail lines is often an added constraint. This paper describes some of the innovative techniques used in the functional design of an interchange at one of the busiest intersections in Calgary, Macleod Trail and 25 Avenue SE. Macleod Trail is an important north-south arterial road, with an average daily traffic (ADT) of 53,000 vehicles trips per day (vpd). 25 Avenue is an east-west through road with an ADT of 17,000 vpd. The paper outlines some of the unconventional options considered, and attempts to rationalize a methodology of alternative selection using a context sensitive design approach.