Buses that have left their route, as it happens. Every position is measured against the journey the bus is running, and one that is further off it than the road there bends is recorded until the bus rejoins. Several buses off route at the same place is something in the road — so they are grouped, and each group is matched against the street works register and the operators’ own disruption feed.
Reading the feed…
Each mark is one incident, at the point the buses got furthest from their routes. Size is the number of buses; red is an incident nothing in either feed explains.
Reading the last two hours of the feed… this takes a moment: it compares every bus that left its route against every live street work in the area.
A bus is called off route when it is further from the line of its journey than that stretch of road bends — measured from the operator’s own published route geometry where there is any, and from a deliberately slack rule based on the distance between stops where there is not. Roughly one operator in three publishes no geometry, and on their routes only a large diversion is caught.
A matching street work is consistent with a diversion, not proof of one, and the distance is shown so you can judge it. A bus off route near nothing may equally be a driver taking a wrong turn, a rail replacement working, or a vehicle running a journey the feed has misnamed — anything more than three kilometres off is treated as the last of those and not recorded at all.
Mileage is only quoted where the road distance between the stops passed is published and the ground the bus actually covered is consistent with it. Where a rejoining bus appears to have crossed more route than it could have driven, the deviation is kept and what it cost is left blank rather than guessed.