Changeable Message Signs (CMS)
The CMS Subsystem is the primary FTMS interface with freeway motorists. The messages on the signs are
controlled by the system operator and the content of the messages is based on the data received from the vehicle detector stations and CCTV camera subsystem. The messages generally advise the freeway motorists of the traffic conditions ahead and suggests
alternative routing which is more time efficient and safer. The messages are displayed at specific locations in order to allow all the freeway motorists to have enough information to select a route when arriving at a decision point.
Each CMS is connected to a CMS controller located in the field cabinet. The CMS controllers are connected to the FTMS Central Computer at the traffic operations centre via the communications subsystem. Using the traffic data collected from vehicle detector stations, the central computer is capable of recommending specific messages on the appropriate CMS.
CMSs within the Highway 401 COMPASS System are primarily used to provide information to motorists with
respect to collector/express diversion, diversion to and from connecting freeways, as well as advising motorists of adverse traffic conditions ahead. The sign display face is made up of 2 full matrix graphics panel with one on each end, plus 3 line
matrices in the middle. The CMS messages are governed by the 3 line and 25 character per line limitation. The number of characters will be reduced by 5 for each graphics symbol panel being activated. A typical Highway 401 COMPASS System CMS has the
following dimensions and specifications:
- 13 metres wide
- 3 metres tall
- 0.5 metre deep
- Each sign weighs approximately 3000 kg
- The display face is composed of two 35 pixels by 35 pixels full matrix panels on each side plus 3 lines of line matrix in the middle with 105 pixels by 7 pixels each. The total number of pixels on each CMS is 4655.
- Each pixel is made up of high intensity amber LEDs (Light Emitting Diodes).
CMSs in Mississauga and Burlington COMPASS Systems are primarily fibre-optic/flip disk technology. This type of CMS works on the principle of exhibiting the message via the light from quartz bulbs which are recessed behind the fibre optic tubes in the sign and by the reflection of car headlight or sunlight. The flip disks have fluorescent tape on one side and black on the other. When a message is exhibited on the CMS, the appropriate disks flip so that the fluorescent side faces the motorists. The disks which are not flipped will have the black side facing out and are designed to block the light from the fibre optic tubes from being visible to the motorist. There are a combination of 2 and 3 lane signs that vary from 20 to 22 characters in width.
Unique to the Burlington and Mississauga COMPASS system are two special walk-in CMSs. The benefits in providing a sheltered environment for maintenance staff to work within the sign are so overwhelming that all future CMSs being implemented in Ontario will be walk-in type.
See also:
- Traffic Operations Centre (TOC)
- Central Computer System
- Closed Circuit Television (CCTV)
- Vehicle Detector Stations (VDS)
- Changeable Message Signs (CMS)
- Ramp Metering Stations (RMS)
- Field Provisions (ducts, cabinets, footings, power, etc.)
- Communications Subsystems:
