"Improving Safety, Efficiency & Traffic Flows In & Around Work Zones"®
Mobile Barriers recommends use of a heavy in-lane shadow vehicle or blocker (eg a dump truck loaded to around 50,000 lbs with signage and TMA) 300’/100m behind the MBT-1 where heavy commercial vehicles comprise a high proportion of prevailing traffic...
"The safety of many short-term, short-duration and mobile work-zone operations is enhanced through the use of shadow vehicles and truck-mounted attenuators (TMAs). Shadow vehicles and TMAs are deployed upstream of these operations to protect work crews on foot from a vehicle intruding into the work space. Shadow vehicles and TMAs also reduce the severity of an impact to intruding vehicle occupants relative to what would likely occur if that vehicle hit work equipment or materials in the work space."
"Those responsible for making decisions on the type of shadow vehicle to use during work operations should begin to consider using heavier shadow vehicles when performing work operations on roadways with significant amounts of high-speed truck traffic. It is important to note that a decision to use a heavier shadow vehicle does require that proper attention be given to the type of TMA used with it so that the consequences of any smaller vehicles impacting the shadow vehicle are not adversely affected. In addition, care must be exercised to ensure that any weight added to the shadow vehicle is properly attached or is otherwise contained within it, so that proper energy dissipation occurs if it is impacted from behind by a large truck. Making intelligent equipment decisions such as this will yield demonstrable increases in worker safety and improve the overall operation of a work site."