No single one of these was deemed best in all circumstances. All involved trade-offs. The device was found to perform as advertised and suitable for use in 60 MPH speed zones. While driver attitudes were favorable to the concept, few carpools resulted from the program. TRF An Investigation of Operational Procedures for Highway Advisory Radio System by Brain Smith et al.
Motorists continue to rely more on commercial radio traffic reports.
This Manual is designed to provide marketing and HOV professionals with practical guidelines for improving the public awareness, understanding, acceptance, and use of HOV lanes and their support facilities. Use of the left shoulder was preferred.