Camera Network – A distinct group of road safety cameras that are networked together and have common communications access.
Communications – The computer network to which Victoria’s road safety cameras are linked. The network allows authorised persons to access the camera remotely to review and download data or perform certain types of testing and maintenance.
Doppler Effect – The change in frequency of a wave as the emitter passes a bystander. The effect is prominent in both sound and radio waves. This is commonly observed when emergency vehicle sirens head towards and then away from an observer. As the siren moves towards the observer, the pitch is higher while the opposite is true when moving away from the observer.
DRCS-P – Stands for ‘Digital Radar Camera System – Parabolic’ and is the name of one of the systems used on EastLink. This system uses a Parabolic Radar to measure vehicle speeds. See the definition for Parabolic Radar, Doppler Effect and Radar for an explanation on how this system works.
Inductive Loop - An inductive loop is a type of in-road sensor used to detect a vehicle’s speed. It consists of a series of electrified wire loops generating a magnetic field embedded in the ground. The magnetic field detects a vehicle’s presence when it travels over it because of the metal in the vehicle. A second loop placed a set distance from the first measures the time a vehicle takes to travel from this sensor to the next.
In-Road Sensors – A vehicle’s speed can be detected by utilising in-road vehicle detectors such as piezos or inductive loops. These sensors detect the presence and speed of a vehicle passing over them. As the two in-road sensors are placed a fixed distance apart, a vehicle's speed can be calculated using the time it takes to travel from one sensor to the other.
Optical Character Recognition (OCR) – A computer-based system that can read letters and numbers. This is used by some camera systems to read vehicle number plates from photographs taken of vehicles. The point-to-point camera system on the Hume Freeway uses OCR.
Parabolic Radar – One of the speed detection systems used on the EastLink. This type of system directs a thin RADAR beam onto a lane to detect vehicles in that lane only. The RADAR is described as parabolic because the strength of the RADAR falls away in the same way as a parabola on a graph. See the definitions of RADAR and Doppler Effect for the basic principles of a Parabolic RADAR.
Piezo - A piezo (piezo-electric) is a type of in-road sensor. When a vehicle travels over it, some of the kinetic energy in the vehicle is converted into electrical energy and these electrical impulses are the presence of a vehicle. As the two in-road sensors are a fixed distance apart, a vehicle’s speed can be calculated using the time it takes to travel from one sensor to the other.
Point-to-Point Cameras – Point-to-point cameras take digital photographs of every vehicle that travels past a camera in the system and calculates the time taken to travel between one camera site and the next. The average speed is calculated in accordance with a formula set out in the Road Safety Act 1986 where the distance between the two road safety cameras is divided by the time taken for a vehicle to travel between the two camera sites. If the average speed exceeds the speed limit, an infringement notice is issued.
RADAR – Uses radio waves to detect and assess the speed of passing vehicles. The radar emits a specific frequency of radio waves. When a vehicle passes through the beam, the radar waves are reflected back with a different frequency. The difference in frequencies is used to calculate the speed of the vehicle using the Doppler Effect.
Secondary Speed Verification (SSV) – The act of using a second speed measurement device or process to independently verify the speed of a vehicle. The two speed measurements must be consistent for an infringement to be issued.
SMD – Speed Measurement Device (also referred to as a Speed Calculation Unit). This is the primary measurement device of a road safety camera and refers to the part or parts of the camera that determine the speed of a vehicle.
SSMD –Secondary Speed Measurement Device. Road safety cameras in Victoria use independent secondary speed measurement devices to verify speeds measured by the primary SMD.