With the proliferation of automated speed and red light camera programs across the county I thought it time to weigh in on the subject. Laser Technology developed and manufactures the TruSense® T-series of laser traffic sensors designed specifically for Traffic Management. This includes speed, vehicle height, vehicle length, and time between vehicles. These versatile sensors can also be used for presence detection for counting or triggering events such as automated red light cameras. Outputs including RS232, RS485, and output triggers allow flexibility to choose the best output for their application.
Life before Traffic Sensors
When the first ‘wet film’ red light camera systems appeared in the U.S. a roll of film (a very big roll) was loaded into a static camera and raised up and down by a pulley system. Presence and speed were detected by either inductive loops buried in the pavement or Piezoelectric strips. The metallic mass of a vehicle could be easily sensed and begins the sequential timing that calculates speed by using two sets of loops (time over distance). However this solution is expensive and subject to ongoing maintenance issues.
The emergence of digital technologies and pixel compression has produced several cameras unique to the automated red light enforcement industry. These cameras essentially superimpose what the creators refer to as “Virtual Loops” in which pixel movement is isolated within these areas and can detect both presence and speed.
Compressive-sensing cameras are an important new class of sensors have different design constraints than standard digital cameras. Not surprisingly, these camera/sensors come with a hefty price tag.
TruSense T Series Offers Improvements
By deploying the TruSense T-Series for red light camera systems the LTI ‘Single Lane’ application assigns two (2) sensors mounted 75 centimeters apart. When a vehicle passes through the beams not only does the laser sensor detect presence but calculates speed as well. Utilizing the beam expanding optics included with the Single Lane System laser sensors “light curtains” are projected allowing full lane coverage. The fast firing rate of 25 kHz ensures each vehicle will incur multiple “hits” to establish total vehicle presence and speed detection.
The traffic sensors can be mounted in a side-fire, overhead, or angled configuration depending on the design requirements and constraints of the installation. Multiple outputs including RS232 and trigger ensure these sensors can be easily integrated and interfaced.
By using the TruSense T-Series single lane sensors RLC providers are able to use ‘off-the-shelf’ digital cameras and AVOID the use of inductive loops or Piezoelectric strips. When you factor in the modest price tag and the reliability Laser Technology is known for, the participating Automated Red Light Camera company will have a huge advantage when writing that RFP.
*This product has been retired in 2022*