How do average speed cameras work?

By Paddy Comyn | May 2024


Average speed cameras have been in use in Ireland since 2017 in Dublin’s Port Tunnel, but they didn’t appear on other roads until 2022. Following an initial trial, they were installed on the M7, spanning from Junction 26 (Nenagh West) to Junction 27 (Birdhill), operating in both directions.  

Now (April 2024) it has been announced that further average speed cameras are set to go live on the N2, N3 and N5 roads this autumn.  

The pilot program for these cameras began in early 2021 but faced several postponements. Calibration and certification delays were cited as primary reasons for the schedule adjustments. 

So how do they work?  

These cameras measure vehicle speeds over a set distance rather than at a single point. This method prevents drivers from slowing only when approaching a camera, promoting a steadier traffic flow. A 2016 UK study indicated a 36% decrease in severe and fatal accidents following the installation of such cameras. 

Average speed cameras were first introduced in Dublin’s Port Tunnel in 2017. Before their installation, over half of the vehicles exceeded the 80 km/h speed limit, with 20% surpassing it by more than 10 km/h. This figure dropped dramatically to 0.15% post-installation. 

Technical Details  

Average speed cameras use Automatic Number Plate Recognition (ANPR) technology to record the time, date, and location of each vehicle that passes through. If a vehicle reaches the next camera too quickly, this information is processed for enforcement, indicating a potential speeding violation. 

These cameras are considered effective in enforcing speed limits, reducing overall travel times, and minimising traffic disruptions caused by conventional speed enforcement methods. Additionally, smoother traffic flow reduces fuel consumption particulate matter and noise emissions. These cameras can’t really be tricked which makes them very effective in slowing down speeders.  

An Garda Síochána is initially implementing the system. Transport Infrastructure Ireland (TII) has yet to announce the exact locations of the new speed cameras on the N2, N3 and N5 roads.  

Penalties for Speeding Drivers caught exceeding speed limits by these cameras face fines of up to €160 and can accrue three penalty points on their license. 


Information correct as of date of publishing. This blog will not be updated or edited so the information may become outdated.