More evidence that most cars and light commercials transiting Bath (Bathampton-Swainswick) already use the toll bridge

In an earlier post, I estimated that nearly half of vehicles transiting Bath between the A36 Warminster Road and the By-pass at Swainswick already used the toll bridge.

In this post, I provide more supporting evidence for this: showing that the split by vehicle types makes sense.

Nearly all heavy commercial vehicles (HCVs) go into town (via Warminster Road and London Road, or vice versa) and then back out again. 

Recall that in these plots, a transit of Bath starts on the left and ends on the right. There's just the thinnest of light blue lines at the top of the diagram for HCVs which are not recorded by ANPRs between Swainswick (south-bound) and Bathampton (Dry Arch). 



The majority of cars and light commercial vehicles that are heading South (see the "Swainswick_S" node on the left) are next recorded at "Bathampton_E" (Dry Arch, leaving Bath). These, we are assuming, use the toll bridge, although a small percentage might have been missed by 2 ANPRs on the way (previously we estimated this 'missed' rate at less than 5%).

Heading North, the proportions are slightly smaller, between 50% and 60%.