A couple of years ago I raised questions about the apparent large gap between the test results for the New Bus for London and the actual fuel economy monitored when it was out ‘on the road’. The reason this is important is because the Mayor has made a lot of the fact that his Boris Bus was the cleanest and greenest of its type.
The results from the Millbrook testing ground appeared to confirm this as every red bus in London has to go through the same journey as the average 159 bus and have all its emissions measured and calibrated.
On the face of it, the New Bus for London does the job. The first 300 buses produced polluted far less than most other hybrid Euro 5 buses and the ones being manufactured now appear to be as good as any other Euro 6.
This is good for the environment and good for Transport for London’s (TfL) finances.
One of the reasons why the New Bus business case produced by TfL appears to ‘stand up’ is because of the edge it has on fuel economy and being green.
The problem is that the greenest bus claims and the Business case only work if you believe the Millbrook test results reflect reality. Having pulled together information about the on the road performance of London’s hybrid buses, I’m having doubts again.
The doubts started in 2013 when the Mayor claimed at City Hall that the Boris Bus did 12mpg, at the same time as Tom Edwards at BBC London reported Transport for London saying that the bus was actually achieving around 6.7mpg on the road.
My sceptical outlook wasn’t helped by the emergence of the Millbrook test certificate which showed that on one of the test runs, the bus managed to do 576mpg with near zero emissions because it ran almost purely on the electric motor.
I accept that this was an aberration, but it did illustrate the fact that the results could change dramatically depending upon how much you used the electric motor during the test. Basically, the more you go electric, the less fuel you use and therefore the less NO2 and PM10 emissions you are likely to have.
In terms of the business case, it doesn’t really matter if there is a gap between the Millbrook results and the reality on the road. As long as you are comparing like with like, then you can work out how much money you are saving. However, it does seem that the New Bus for London has a bigger gap between test and reality than any other bus.
When the Euro 5 NBfL was re-tested and the results scaled back, it still managed 10.8mpg, compared to the best of the other hybrids which achieved between 8 and 9mpg.
When they were monitored on the road, covering 4 actual routes, the NBfL was managing between 6.2 and 7.4mpg. That compares with the hybrid fleet average of just over 7mpg. Put simply, the Boris Bus was either dramatically under-performing in real life, or significantly over-performing on the test track.
Having seen the latest tests from Millbrook, the Euro 6 buses could well repeat this pattern. The average of the ordinary Euro 6 buses is 9mpg, while the Euro 6 Boris Bus is doing 13mpg. Of course, the on the road monitoring may show that (this time) the reality matches the test results. If that is true then the business case may stack up. If they don’t, then the already very marginal gains for Euro 6 Boris buses illustrated in the business case simply don’t add up.
The next Mayor needs an independent audit of the New Bus for London to get to the truth of what the benefits really are and whether the downsides have been deliberately underplayed in order to justify a project which never should have been given the green light.
Darren Johnson represents the Green Party on the London Assembly.
