Interchange Justification Studies/Interchange Modification Studies
Purpose of an IJS/IMS
Control of access on the Interstate and other freeway systems is considered critical to providing the highest quality of service in terms of safety and mobility. Sometimes referred to as an Access Point Request, these studies are needed on Interstate and other freeway systems in accordance to Federal Code 23 U.S.C. 111 and FHWA Policy - Additional Interchanges to the Interstate System (Federal Register: February 11, 1998, Volume 63, Number 28).
The documentation required depends on the type of change requested - new or revised. New Access is the addition of a point of access where none previously existed. This includes the construction of an entirely new interchange such that it will result in additional points of access or additional ramps to existing interchanges. As an example, the reconstruction of an existing diamond interchange to a full cloverleaf interchange would add four new points of access.
Revised Access is the revision of existing ramps or crossroads within the limited access area such that the number of access points will remain the same but the operation and/or safety of the Interstate/freeway system may be affected. The changing of a cloverleaf interchange to a fully directional interchange, the adding of turn lanes at crossroad-ramp intersections, the adding of through lanes on the crossroad through an interchange, or the widening of a single lane entrance ramp to two lanes are considered examples of revised points of access.
New or revised access point requests require the preparation and processing of an Access Point Request Document. Generally, a new access requires an Interchange Justification Study (IJS), and a revised access requires an Interchange Modification Study (IMS). Ultimately, the study is going to demonstrate that the modification to the Interstate will not degrades its capacity or safety.
There is a prequalification requirement for consultants who want to prepare interchange justification and modification studies (more info...)