Are Variable Message Signs effective?

Dhaval Desai, Managing Director, Trafitek Solutions Pvt Ltd, explained, “Variable message signs (VMS) are traffic control devices that provide motorists enroute traveler information. The objective of providing the information is to allow the motorist time to avoid an incident, prepare for unavoidable conditions, or to give travel directions. For all displayed information, the goal is to have a positive impact on the motorist’s travel time.”

Application

Variable Message Signs are commonly installed on full-span overhead sign bridges, post-mounted on roadway shoulders, and overhead cantilever structures. The information is most often displayed in real-time and can be controlled either from a remote centralised location or locally at the site. The message signs are designed to affect motorist behaviour to improve traffic flow and operations. Traveller information displayed on VMS may be generated as a result of a planned or unplanned event, which is programmed or scheduled by operations personnel.

VMS are essential in both urban and inter-urban areas; they are designed / deployed based on the usage. In urban areas, VMS specifications are designed to meet slow moving traffic and also cater to some extent to the pedestrians. Whereas on highways the traffic is fast moving, and hence the specifications of VMS in terms of resolution, clarity, size etc has to meet these requirements. In urban areas it is important to have message signs deployed at critical intersections and important nodes of a corridor. It should primarily inform about travel information such as distance/time to the airport or any important city landmarks/locales, any road closures/ diversions or sometimes any security related information to safeguard people.

On highways, the VMS may be used for lane control messaging, speed enforcement display, weather related messages, accidents etc so that the motorist is prepared for it. VMS are an essential interface with the road user guiding him/her during his/her journey to make it safe and better. It can help in saving lives by informing motorists to drive slowly or to avoid certain turns or a very bad weather of poor visibility etc.

Types of VMS

There are various types of VMSs: permanent VMS unit, portable VMS unit and truck-mounted VMS unit for a specific purpose. Each type has advantages and limitations for use.

Permanent or Stationary VMS: This is mounted on overhead structures either spanning the roadway, cantilevered out over a portion of the highway, or off the highway, and is used to influence motorists for traffic control purposes. The messages can be manually, mechanically, or electromechanically changed to provide motorists with information about traffic congestion, traffic crashes, maintenance operations, adverse weather conditions, roadway conditions, organized events, or other highway features (e.g., toll booths, weigh stations, etc.). A benefit of permanent VMS is that it can support a longer, more detailed message and afford the greatest exposure time for motorists to comprehend messages before arriving at a decision point.

Portable VMS or PVMS: This is typically trailer mounted; self powered, easily moved and placed near the decision point on the highway right-of-way. PVMS messages can be changed by either manual, mechanical or electromechanical means to provide motorists with information about traffic congestion, traffic crashes, maintenance operations, adverse weather conditions, roadway conditions, organized events, or other highway features (e.g., toll booths, weigh stations, etc).

Truck-Mounted VMS: Generally a small unit, mounted at or near the rear of a truck, this has limited message space and font sizes. The message limitations commonly result in the use of graphics such as arrows to improve motorist comprehension and support a narrower range of ATM activities.

VMS is often used for different applications other than its customary applications, such as to advise motorists of information about traffic congestion, traffic crashes, maintenance operations, adverse weather conditions, roadway conditions, organized events, or other highway features (e.g., arrow boards/panels used to display advisory text information verses a flashing graphic arrow).