flow × flow vs own average
Traffic in the selected window against that road's own average hour on a typical weekday (Tue–Thu). 1.0× is average, 1.5× is half as busy again. It measures shape, not size — every road is compared only to itself.
delay % vs free-flow
How much slower traffic moves than the road's free-flow speed (its 98th-percentile observed speed). 0% is unimpeded; 25% means average speeds a quarter below free-flow. Catches slowdowns that flow alone misses, e.g. smart-motorway speed limits.
vs GB, same window
The road's flow index divided by the all-GB average for the same days and hours. Above 1× = busier than the national picture at that time; below = quieter.
vs typical weekdays
Shown on the Bank holiday day type: holiday flow as a percentage of normal weekday flow at the same hours. −25% means a quarter less traffic.
k veh/day AADT
Annual average daily traffic, both directions, from DfT counts — the absolute scale. DfT covers all of GB, including Scotland and Wales.
day-hours observed
How many day-samples back the chart. Big numbers = solid signal; hours with too few observations are dropped rather than shown misleadingly.
map colour
Blends flow index and delay for the selected window: green = quiet and free-flowing, red = busy and slow. Road width follows traffic volume (AADT).
best / worst windows Best times tab
3-hour windows ranked by a blend of low flow and low delay across the days you've selected. Tap one to load it on the map.
holiday Δ% Holidays tab
Daily traffic on the holiday vs the same weekday outside holidays, pooled across all years. Negative = quieter than usual.
day types
Mon, Tue–Thu and Fri behave differently, so they're separate. Bank hol covers bank holiday Mondays; Xmas spans 20 Dec–2 Jan; Easter spans Good Friday–Easter Monday.
data & method
Sensors: National Highways WebTRIS (England's strategic road network), 15-minute data from sampled weeks of 2019 and 2022–2024, medians across years so roadworks and outliers don't dominate; COVID years excluded. Magnitudes: DfT road traffic statistics (GB-wide). Roads outside England show DfT annual data only. Updated quarterly.