About
Where the data comes from, how the estimates are made, and what the site does not know.
Data sources
Traffic data is published by the Department for Infrastructure (DfI) through TrafficWatchNI. The site reads the same public endpoints the official site uses: journey times, roadworks, incidents, weather stations and camera images.
Baseline demand comes from the DfI permanent traffic counter dataset on Open Data NI, published under the Open Government Licence. It gives annual average daily traffic, HGV share and peak hour flows for around 90 counter sites.
Method
Journey times are published as whole minutes. Speed is derived from segment length, and flow is estimated from speed using a triangular fundamental diagram: below about 72% of free-flow speed the road is on the congested branch and flow is recoverable; above it, speed does not determine flow, so no figure is shown.
Forecasts blend the current observation with a typical-week demand profile, reverting toward normal over 60 minutes. The profile is a standard UK shape, not measured Northern Ireland data, so treat forecasts as indicative.
Segment lengths come from approximate junction coordinates. Where a derived length implies an impossible speed, the model clamps to the observed time and flags the segment rather than reporting a figure it cannot support.
Limits
Journey times cover the M1, M2, Westlink and A1 only. That is 31 segments, not the whole network. Camera images are 640 by 352 pixels and update roughly every five seconds, which is not enough to count vehicles.
Accessibility
The site targets WCAG 2.2 AA. Text meets contrast requirements in both themes, every control is reachable by keyboard, focus is visible, and the map has a text alternative in the segment table below it.
If something does not work for you, the contact address below is the fastest route to a fix.
Contact
This is an unofficial prototype and is not affiliated with DfI. For the official service, use TrafficWatchNI.