In 2013, Caltrans unveiled the barrier transfer machine, or “zipper,” on I-15. It moves slowly at about 8 miles an hour, but it can help drivers move faster by increasing the amount of lanes from two to three in one direction. Drivers in the other direction would only get one express lane..
By expanding the work zone during off-peak traffic periods, contractors can combine or eliminate stages and use larger, more efficient equipment to accelerate the construction process. This often results in eliminating one or more construction seasons. The system also reduces congestion by enabling more lanes to be open during peak hour traffic. For partial width construction, one side of the road can be completely closed for construction while all traffic is diverted to the other side, with a moveable median barrier reconfiguring the roadway in real time to provide more lanes in the peak direction.