Off-road Retrofit Safety and Exemptions

This page last reviewed May 26, 2017

If exhaust retrofits are installed so as to block a vehicle operator's visibility, they can pose a potential safety hazard. ARB and Occupational Safety and Health Standards Board (OSHSB) staff worked together over several years to address retrofit visibility concerns for off-road diesel vehicles. At the OSHSB December 15, 2011, hearing, OSHSB approved a regulation regarding exhaust retrofit visibility. The approved safety order is also available at the bottom of the OSHSB hearing page. In summary, there cannot be obstruction of operator's view outside a rectangle drawn on the ground 40 inches from the machine's perimeter.

If an exhaust retrofit can be installed underhood without altering the engine cover, that installation would satisfy visibility issues. Other acceptable installation locations are those contained within the operator's sight lines to the machine edges.

Because exhaust retrofits are no longer mandatory for compliance with the off-road regulation, vehicles in large and medium fleets will no longer be assessed for an exemption from the off-road regulation. For small fleets, per section 2449.1(b)(3), a vehicle may be exempt from BACT if there is not a retrofit available, or a retrofit cannot be safely installed 10 months prior to the compliance date. The initial compliance date for small fleets is January 1, 2019.

Example Installations With No Visibility Impairment

The vehicles listed below are examples of vehicles that have been retrofitted in a manner that does not block the line of sight of the operator. There are other methods in which the vehicles could be retrofitted without impairing visibility.
Vehicle Engine Description Pictures
2008 Caterpillar 938H
180 Hp 2008 Cat 6.6
ECS Purifilter:
Underhood installation.
2006 Prinoth BR350
Dual Cat C9s; 335 hp and 350 hp
ECS Purifilter:
Underhood installation.

Vehicles Not Able To Be Safely Retrofitted

Prior to February 2012, it had been determined that certain vehicles could not have a retrofit safely installed without violating the interim retrofit visibility policy. That interim retrofit visibility policy is no longer in place. Hence, the previous (temporary) exemptions shown on the interim visibility policy exemptions page are no longer valid, and if exemptions are still needed for those vehicles, they need to be reassessed using the current OSHSB safety order.

Back to the homepage for the off-road diesel vehicle regulation.