Truck-Mounted Attenuator (TMA) requirement
WSDOT does not require the use of TMAs but they are highly recommended for many work operations.
For WSDOT construction projects TMAs are routinely included as a per each bid item in the contract. If there is an additional bid item for the hourly operation of the vehicle, special provisions are included in the contract documents. Typically a TMA is included in the contract for a high-speed, high-volume project. They work great for isolated work operations but can be difficult for projects that have multiple work operations going on concurrently or paving projects where the TMA cannot drive on the hot mat. WSDOT show typical locations in the contract plans where a TMA or protective vehicle would be recommended but ultimately it is the contractor’s decisions on where and how he prefers to use the vehicle. Recently they have made recommendations that for paving projects the TMA be specifically used to provide protection for materials testing at the end of the paving train. Often the truck operator is left unprotected (yet still in a closed lane) far away from the paving operation so they felt this was an area that could benefit from the added protection.
For WSDOT maintenance work operations they also do not require TMAs to be used but many of these operations are great candidates for using one or in some instances more than one. TMAs have become a common part of the WSDOT maintenance work equipment in recent years, especially in the more urban areas along Interstate 5 where they have proven their benefit on more than one occasion. Typically the TMAs are used in situations where the work is short duration or a mobile type operation and at a specific location such as guardrail repair, pot hole patching, striping, rpm installation, etc. and the TMA will shadow the operation. They have several typical traffic control plans that have been developed that illustrate typical TMA placement during these operations.