Redefining journey time reliability for National Highways with end-to-end traffic data
Success Story
National Highways focuses on making journeys safer, smoother and more reliable across all motorways and major roads in England. To improve how it communicates journey time reliability with the public and better understand overall road network performance, it joined forces with TomTom and AtkinsRéalis. Together, the teams developed a clearer, more meaningful reliability metric.
National Highways’ existing metric was considered too complex for public understanding. It reported reliability per section of road, measuring the difference between observed and profile travel times in seconds per vehicle per mile. This approach didn’t reflect how road users make decisions about their journeys. Drivers don’t think in seconds per mile or about the reliability of sections of road — they think about end-to-end journeys. Pressure groups echoed this sentiment, pushing for a metric that could be easily understood and trusted by the public. That’s where TomTom and AtkinsRéalis came in.
Building clarity across the road network
National Highways, together with TomTom and AtkinsRéalis, developed a new journey time reliability metric that is centered on end-to-end journeys rather than small road segments.
The new metric shows reliability as the percentage of journeys that fall within a predictable range of journey times. A predictable range is based on the modal (most frequent) journey time value for any time of day, within an acceptable level of variability. The complete, data-rich solution includes:
Route-level reliability rates
National aggregate rates
Additional traffic and road travel statistics
Dashboards to monitor performance
Making the solution possible, TomTom’s Traffic Stats product provides comprehensive end-to-end journey data across the road network. TomTom’s full-traversal capabilities were crucial to overcoming the difficulty of accurately tracking an entire trip's travel time — uniquely delivering the right data where other traffic data providers in the market fell short, only able to supply segment-specific travel times. Putting it all together, AtkinsRéalis ensured the solution aligns with best-in-class transport planning and technical standards. The new metric has been live since April 2025.
Delivering more than a meaningful metric
National Highways now provides clearer, more accurate and useful data on journey time reliability. As a result, the solution speaks to road users in a language they understand, enables more targeted reliability improvements and informs smarter operational decisions. The new metric has passed internal validation and is in active use, positioning National Highways as a leader in data-driven, customer-focused transport management.
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Richard Fernandes, Technical Director
AtkinsRéalis