This link offers 29 free courses on Traffic Engineering:
Traffic Engineering Review
These courses are offered by ADA, the National Highway Institute, and the Federal Highway Administration.
Books for the Transportation Exam:
1. Transportation Depth Reference Manual for the Civil PE Exam
2. Transportation Review Books for the Civil: Transportation PE exam
3. Traffic Engineering Handbook
4. For a free list of Transportation Engineering equations, see this 107-page free pdf from Shahin Monsour.
5. I waded through the mass of offerings and did all the creative searching. I compiled the best of the legitimate PE exam study materials on this page: PE Exam Books Civil Transportation.