I just passed the PE and all of my experience is with a traffic engineering consulting firm. I had no problems whatsoever. If he is more of a planner than an engineer then maybe that's why.
I work for a traffic firm but we also do Civil Engineering which I am not involved in. Typically a traffic consulting firm does
Traffic Engineering
Traffic Signal Engineering and System Synchronization
Traffic Impact Study and Parking Study
Traffic Calming and Pedestrian Safety Study
Traffic Control and Detour Design
Intelligent Transportation System (ITS)
I also do
Electrical Engineering
Roadway Lighting and Control Design
Streetscape and Landscape Lighting Design
Power Design and Planning
Could I see a sample of the wording used for your application? He is both a planner/designer. We do electrical and communications, its design, and other traffic related design.