Guest Post: Can we fix the sharp rise in bus and other traffic delays since 2010?

Can we fix the sharp rise in bus and other traffic delays since 2010?

Guest post by Rob Shepherd*

This post complements Rob Shepherd’s previous contribution: ‘Cutting transport emissions in Brighton and Hove: what is a priority and what is not?’ .

Why have main road traffic delays in Brighton and Hove risen so sharply since 2010, despite less traffic?

Why does the A259 morning bus commute take longer than before the bus lane was created in 2008?

Why do most peak time bus journeys take about 30% longer than in 2010?

Answer. Reducing the width of critical road lanes from 4.5m to 3.0m reduces road capacity: the Department for Transport warns that this could be by as much as 30%.

Why are 3.0m lanes so much worse?

A bus is 2.5m wide, so a 3.0m lane does not let other traffic pass a bus at a bus stop. Also a vehicle waiting for a gap in the traffic so it can turn right, blocks the following traffic (there is no room to pass inside). With 4.5m lanes, there are no such delays.

Without passing points (e.g. layby bus stops or breaks in an adjacent bus lane) this impact is inevitable, and, as bus services become more frequent, the delays grow. 

The reduction in road capacity also makes roads more vulnerable to other delays, such as pedestrian operated crossings (pelicans and toucans), whose frequency of use can also grow with bus frequency (because of the associated growth in use of nearby bus stops).

Apart from the economic damage, the air pollution, and making bus services less attractive, this situation is very wasteful of CO2e.

However, until we accept the causes of the problem, we will not reduce the waste. 

The A259 traffic capacity problem near Rottingdean

During the 2005 peak hours, some 1600 vehicles passed Eastwards through Rottingdean Junction. This figure dropped year on year to fewer than 1200 vehicles by 2019.  Blue line in the chart below.

This drop was not because the junction’s capacity was reduced. In fact it was increased in 2008.

It is not because traffic volumes fell 30%. They fell a little (15%, the brown line in the chart above), but at peak times there are still hundreds of vehicles queuing. In fact, typical queues of 170 and 342 vehicles waiting to go East were measured in 2015 and 2017 respectively. 

At the same time, bus journeys took up to 30% longer. Bus timetables show this; and the bus company blamed a recent rise in fares on its extra operational costs caused by the delays.

The Big Question. Why are there such big queues, why doesn't more traffic pass through the junction and why does less and less traffic pass through the junction, year on year?

Answer. The throughput dropped in 2008 when the road was narrowed to fit in the bus lane. The narrow road to the East of the junction can only let about 1200 vehicles pass, or even fewer when the flow is restricted by pedestrian crossings and other things that reduce the flow.

So, there is no mystery about the long peak time queues on the A259 growing at the same times as traffic volumes fell; or bus delays getting even worse as bus frequency increased. The only mystery is why the predictable was not predicted and planned for.

There is a solution: open the East-to-West bus lane. to general traffic This would stop right-turning traffic delaying non-priority traffic and reduce the queue that blocks buses (until they reach the bus lane sections). The bus lane’s spare capacity will handle this without causing delays. This is simple and very cheap (just signage).

Can we find similar quick wins for the A259 West-to-East traffic or North Street or the City’s other congestion hotspots?  Probably nothing so simple, but we should look.

 Photo: https://britishbeaches.uk/saltdean-beach-east-sussex-england/photos/4758

*This is a guest blog by Rob Shepherd. Rob is a retired mathematician who has studied local traffic congestion, air pollution and carbon emissions, as well as our Council’s record in these areas.

Perspective pieces are the responsibility of the authors, and do not commit Climate:Change in any way. Guest posts are published to explore issues or stimulate debate. Comments are welcome.