Traffic Management

A moveable section of concrete barriers used to separate traffic on multi lane highways. Zipper barriers are used along Interstate H1 on Oahu and Interstate 66 across the Potomac River, among other locations. Use of these barriers reallocates a westbound lane for the eastbound / morning commute and vice versa during the evening. A barrier transfer machine moves the barriers.

Also known as a port of entry or check station out west, a weigh station constitutes a set of scales located alongside a freeway that verifies that trucks and buses are within the legal weight limit. Hours of operation and limits vary from state to state. Weigh stations are commonly located near state lines, but they may be found scattered throughout the highway system within the state.

Variable message signs (known as VMS) are electronic signs that can be modified to inform motorists of changing conditions. These are commonly used for displaying travel times to the next exit(s), alerting motorists of forthcoming traffic accidents and congestion, advising the public about ongoing Amber and Silver Alerts, indicating construction related closures and lane shifts and warning of severe weather. They are usually operated by a traffic operations center.

Refers to a traffic light assembly where the signala are supported by a wire spanning the distance of the roadway width. These are less expensive than their mast arm supported counterparts, but are less wind resistant.

One to three lane carriageways that flow one direction during the morning or inbound commute hours and the opposite during the evening or outbound peak travel times. These are separated from the general travel lanes by a physical barrier, with entry points closed by barricades or movable gates to prevent wrong-way crashes. Interstate 64 in Norfolk and Virginia Beach and the Express Lanes for I-5 in Seattle, Washington both incorporate [...]

Some on-ramps are governed with a traffic control device to regulate the flow of merging traffic onto a freeway. Ramp meters are commonly found in urban and metropolitan areas and are used to aid in maintaining travel speeds on freeway mainlines. Queues from the ramp signals may result in traffic back ups onto nearby surface streets.

These traffic light assemblies are more wind resistant and expensive than their span wire assembly counterparts. Mast arm assemblies support traffic lights on a metal pole and mast. Western states used these historically because of their durability to withstand an earthquake, but now their use extends nationwide.

A set of electronic signs displaying either a green down arrow or a red letter X indicating whether a travel lane is open or closed. These are generally found on major bridges in the Northeast, where lanes may be adjusted during the respective peak hours to allow for an additional lane in one direction at the expense of the other. Additional uses include commuter based arterial routes, such as U.S. [...]