Requirements for work or shadow vehicles to have Truck-Mounted Attenuator (TMA)
Caltran’s policy for maintenance operations is as follows:
When closing a lane, a barrier vehicle or a shadow vehicle shall be used for the installation of the signs and the FAS if they can be placed while off the traveled way on the shoulder or median. A shadow vehicle or a barrier with a Truck Mounted Crash Cushion (TMCC) shall be used as the protective vehicle during the installation and retrieval of traffic cones and signs in the taper and tangent sections of the lane closure. All devices placed in areas with no shoulders from an open lane require the use of a shadow vehicle for protection.
Any slow-moving unshadowed vehicle working in a freeway lane outside a lane closure shall have a Truck Mounted Crash Cushion (TMCC) and a Flashing Arrow Sign (FAS) or it shall be followed by a shadow vehicle. The only exceptions to this rule are tow trucks and snow removal/de-icing equipment.
The definitions of a shadow vehicle and barrier vehicle are:
A shadow vehicle is used to protect the work vehicle in a moving operation. A shadow vehicle shall: (1) Have a TMCC; (2) Carry a FAS operating in the arrow mode while occupying a lane on multilane roads; (3) On two lane roads, carry either a FAS operating in the caution mode or a flashing amber light; (4) Be equipped with headrests; (5) Be equipped with seat belt and shoulder harness; and (6) Be equipped with a two-way radio.
A barrier vehicle is an unoccupied vehicle or piece of equipment used to protect workers from errant motorists. Any vehicle at a work site can be used as a barrier because there is no minimum barrier vehicle size. However, workers shall use the heaviest vehicle reasonably available. In certain instances, more than one barrier vehicle may be needed. A barrier vehicle does not require a TMCC. However, if a TMCC is available, it should be used.
**Caltrans has adopted the MUTCD with a CA Supplement and has changed from the term TMCC to Truck-Mounted Attenuator (TMA). However, the policy stated above will remain in place for maintenance forces.**