Average Speed Over Distance (ASOD) cameras are an increasingly popular form of traffic enforcement that has a proven record of reducing vehicle accidents.
On the N1 highway, for example, the introduction an ASOD system saw speeding cases from from 586 incidents per month to 362 per month over a four-year period.
Despite this, they are still relatively uncommon and are only found in a few provinces along major routes, while most other roads are still monitored by police speed traps.
How they work
Average Speed Over Distance systems make use of two cameras set up at the start and end of a section of a variable length of road.
The system then calculates how long it is expected to take to journey from the start of the monitored area (point A) to the end of the track (point B) based on its assigned speed limit.
For example, a 100km stretch of road with a speed limit of 100km/h (27.7 metres per second) should take exactly one hour, if no unforeseen hiccups arise.
If a motorist is doing 120km/h, they will reach point B faster than the expected one-hour timeframe, whereupon the system will use a time-over-distance formula to work out that the individual was averaging 33.3 metres per second and issue a fine.
The touted benefits of ASOD, according to Arrive Alive, are as follows:
- Change in driver behaviour
- Vehicle and driver compliance
- Drastic reduction in vehicle speed
- Higher visibility of traffic enforcement
The system is also considered to be fairer as it removes the “gotcha” aspect of hidden speed traps because ASOD areas are highly visible and motorists are given an advanced warning before entering.
Furthermore, the increased monitoring area is beneficial to law enforcement as it can alert traffic officers to offenses registered on the National Traffic Information System (Natis), such as expired licenses or outstanding vehicle roadworthiness certificates.
Where they are
ASOD systems are currently in use in the Free State, Kwa-Zulu Natal, and the Western Cape. Gauteng has expressed interest in converting the gantries from its failed e-toll scheme to average-speed enforcement, but has yet to do so as of the time of writing.
Western Cape
- N1 – Laingsburg to Towns River
- N1 – Leeu Gamka to Lainsburg
- N1 – Beauford West to Leeu Gamka
- N1 – Three Sisters to Beauford West
- N2 – Sir Lowry’s Pass to Houw Hoek
- M3 – University of Cape Town to District Six
- R27 – Ganze Kraal to Saldanha
- R61 – Aberdeen to Beauford West
Free State
- N3 – Warden to Villiers
- N3 – Harrismith to Warden
- N3 – Van Reenen to Harrismith
Kwa-Zulu Natal
- N3 – Van Reenen’s Pass (southbound only)
- N3 – Roosboom to Togula Plaza
- N3 – Hidcote to Roosboom
- N3 – Tweedie to Nottingham Road (southbound only)
- N3 – Cedara to Tweedie
Keyword: Speed-over-distance cameras in South Africa – Where they are and how they work