Cities hire Minagar & Associates, Inc. for on-call traffic engineering, signal design and timing, interconnect, striping, traffic impact review, and Safe System / Vision Zero plans (SS4A, LRSP, SRTS, E&TS).
Colton is a published municipal example: city traffic engineering, signal PS&E, plan check, inspection, and freeway off-ramp studies. See City of Colton projects and the traffic engineering gallery.