Traffic Cameras

Effective implementation of Intelligent Transportation Systems (ITS) depends on timely, reliable, and comprehensive information on traffic conditions. Closed-circuit television (CCTV) monitoring of the roadway network is one of the best mechanisms for providing this information to a transportation management center (TMC).

CCTV cameras provide the following functions:

Allow operators at control center to directly observe traffic conditions on the INFORM roadways.
Verify incident and congestion conditions determined by central computers.
Allow system equipment performance to be observed. This includes VMS, HELP vehicles, ramp meter signals and traffic signals within field of view.
The monitoring system for the Southern State Parkway, as currently planned, includes sites for at least 45 CCTV cameras with pan, tilt, and zoom (PTZ) capability.

The INFORM system, as of 2001, consisting of the island's northern corridor and limited portions of the busiest north-south connecting routes, includes 84 CCTV cameras.

Variable Message Signs

Variable message signs (VMS) will be located at key points on the corridor highways and connecting routes. Traffic information coordinators will use data obtained from computers to assess the volume and speed of traffic on different sections of the highways. They will be able to immediately spot delays and transmit appropriate advisory messages to motorists via VMS.

The minimum required information on variable message signs will include a statement of the problem and an action statement.

Sequential message components must be prioritized to meet clearly identified motorist information needs to make decisions. Advisory sign messages may consist of the following elements:

• A problem statement (accident, roadwork, icy road, etc.).
• A location statement (where the problem is located in relation to the motorist and/or to an exit/diversion point).
• An effect statement (lane closure, delay, chains required, etc.).
• An attention statement (addressing a certain group of motorists or destination).
• An action statement or statements (what to do).

Message Types

There are four general categories of incident conditions that LI ITS variable message signs will convey to motorists:

• Non-recurring congestion (accidents)
  
• Construction
  
• Environmental conditions
  
• Special events
  

When Messages Are Issued

The impact of an incident on motorists depends on the time of day the incident occurred, the expected duration, and the roadway capacity lost.

• Local incidents potentially affect motorists in the immediate area of the incident. These incidents typically have low severity and short duration, e.g., a stalled car or a minor fender-bender.
• Regional incidents potentially affect motorists in the immediate area of the incident and may result in long delays upstream. These incidents may be typically moderate to high in severity and duration, e.g., accidents resulting in injuries or hazardous material spills.
• Corridor incidents could potentially affect motorists along the entire corridor and could require the coordination of all the transportation agencies within the corridor. These incidents are extremely high in severity and incident duration, e.g., a major snow storm or a bridge collapse.

Regardless of the severity of the incident, the information given to motorists depends on their location relative to the incident. The primary motorist information zone is defined as that area in the immediate vicinity of the incident where there are no major alternate routes available in the direction of travel to divert traffic. Messages within this zone cover the direction and location of the incident, the nature of the problem, the duration of the delay, and special driving instructions.

Secondary motorist information zones are defined as those areas outside the primary motorist information zone where there are one or more alternate routes available to divert traffic. This zone extends outward to the last vehicle influenced by the incident. The extent of the area will vary according to the severity of the incident. The messages within this zone cover the direction and location of the incident, the nature of the problem, the duration/extension of congestion and travel time between fixed points and suggested alternate routes