Automatic Vehicle Identification Systems for Electronic Toll Collection

Accessibility Assistance: Caltrans makes every attempt to ensure our documents are accessible. Due to variances between assistive technologies, there may be portions of these documents which are not accessible. Where documents cannot be made accessible, we are committed to providing alternative access to the content. Should you need assistance please contact us at (916) 654-2852 or visit Request ADA Compliant Documents.

California Law requires Caltrans, in cooperation with the state's toll facility operators, to develop functional specifications and standards, i.e., a protocol for automatic vehicle identification (AVI), which would be used for electronic toll collection (ETC). The protocol governs the features of transponders in vehicles and overhead devices (readers) which detect the transponders. California law requires any protocol selected to be an open standard, meaning that toll facility operators must have the ability to select ETC equipment from different manufacturers and vendors.

In 1992, Caltrans developed a protocol for ETC in California which became known as "Title 21" after the section of the California Code of Regulations where the specifications for the standard are listed. Effective January 1, 2019, Caltrans adopted a new protocol known as 6C. The existing Title 21 protocol will continue to be used for five years after that date, and then be discontinued. The five-year overlap with the two protocols is intended to give the toll facility operators the necessary time to eliminate their existing inventory of the Title 21 transponders.

California 6C Electronic Toll Collection Standard (PDF)

Compatibility Specifications for Automatic Vehicle Identification Equipment

Automatic Vehicle Identification Specifications Proposed Rulemaking

Caltrans is currently considering the development of a regulatory change that will impact the Title 21 protocol.

Currently, all agencies that utilize AVI are required to discontinue using and supporting the Title 21 protocol on January 1, 2024. Caltrans has received a proposal to change this date to January 1, 2027.

Pre-Notice Public Discussion

In response to this request, Caltrans provided a questionnaire to all potentially affected stakeholders and held a public workshop on February 28, 2023, to obtain initial comments. The responses to the questionnaire and the minutes from the workshop are provided below.

Questionnaire Responses

Title 21 Public Workshop Minutes

Automatic Vehicle Identification Specifications Proposed Rulemaking Package