Purpose
This safety advisory serves as a reminder to ensure that the brake interlock system is regularly checked and properly maintained to prevent unintended brake application while the vehicle is travelling.
Disclaimer
This page does not change the Transportation of Dangerous Goods (TDG) Regulations.
Scope
This safety advisory is for users of dangerous goods highway tanks equipped with brake interlock systems that prevent vehicle motion during loading and unloading of dangerous goods.
Regulatory requirements
Part 5 of the TDG Regulations requires that highway tanks transporting dangerous goods comply with Canadian Standards Association (CSA) standards adopted therein. The CSA B621 and CSA B622 standards referenced in subsections 5.10 (11) and 5.14 (2) of the TDG Regulations are the selection and use standards for highway tanks transporting dangerous goods by road in Canada. CSA B621 covers class 3, 4, 5, 6.1, 8, and 9 dangerous goods and CSA B622 covers class 2 dangerous goods.
These standards require that highway tanks be prevented from moving during loading and unloading of dangerous goods. This can be done using wheel chock blocks or using an integrated brake interlock system that activates the vehicle brakes. The choice provides highway tank operators with the flexibility to select the best method for their operations.
The general loading and unloading requirements for highway tanks transporting dangerous goods are found in Clause 7.1 of CSA B621-14 and Clause 5.1 of CSA B622-14. The abbreviated clauses are shown below:
From CSA B621-14:
7 Use of means of containment
7.1 General requirements
A means of containment shall not be used unless the following conditions are fulfilled:
...
(h) while parked for loading or unloading,
(i) a fail-safe brake interlock system is used that will apply the parking brake while the loading and unloading hoses are connected; or
(ii) chock blocks are used at the wheels.
From CSA B622-14:
5 Loading and unloading requirements
5.1 General requirements
A means of containment shall not be used unless the following conditions are fulfilled:
...
(g) while parked for loading or unloading,
(i) a fail-safe brake interlock system is used that will apply the parking brake while the loading and unloading hoses are connected; or
(ii) chock blocks at the rear wheels;
Some older vehicles with mechanical brake interlock systems activate the interlock through an air valve connected to a cabinet door (or sometimes a gate) that houses the loading and unloading connection points of the tank. When the door or gate is opened to load and unload product, the air valve is opened and air from the braking system is released, applying the vehicle brakes.
Many newer brake interlock systems are designed to activate only when the vehicle is stopped and therefore, could not apply the vehicle brakes if the loading cabinet door or gate were inadvertently opened while moving.
It is important to note that brake interlock systems are not exclusive to highway tanks in dangerous goods service. They are also found on other heavy vehicles.
Transport Canada recommends that highway tank owners with brake interlock systems periodically verify that their systems are in good working order, and that all components of the system are securely connected to the vehicles and adjusted properly.
Questions
If you have any questions, please contact our Transportation of Dangerous Goods Directorate, Regulatory Frameworks and International Engagement Branch:
Email: MOCRegister-RegistreContenant@tc.gc.ca
Phone: 1-855-298-1520 (toll free)