Regular readers might recall the age it took TfL to reply to a simple FoI about prototype NB4L fuel consumption – we still don’t know what it was, but they did eventually tell us, and in a press release all the transport journalists in London, the following:

  • the prototypes have achieved a fleet average of 6.74mpg in recent weeks
  • double deck hybrid buses operating on route 73 are achieving 6.1mpg

This was duly picked up as gospel by the BBC and Guardian (note amendation at the bottom after yours truly contacted Gwyn Topham and pointed out TfL were bullshitting him, and he creditably went back and queried it) and appears to be the official PR position now.  Unfortunately for TfL their PR line has been thoroughly undermined a bit by, well, TfL, in the form of Mike Weston’s annual presentation to the European Hybrid User Forum in Barcelona earlier this month.  They always put the slideshows on line and this year reveals that TfL do indeed collect detailed statistics on hybrid fuel consumption on a per route per vehicle basis and have been preparing a report based on field studies during February-May 2013.  The snippet in the slideshow makes very interesting reading in the light of the above:Hybrid-MPG

Note well – the average mpg for both the series ADL E400H and parallel Wright/Volvo B5LH come out pretty much the same at 7.2mpg.  Note also the wide variation on routes, which makes one wonder what the hell they were doing comparing 38s and 73s in the FoI response.  In fact, let’s work out the range:

  •  ADL E400H – 6.89 to 7.55 mpg (best is 9.5% better than worst)
  • Wright/Volvo B5LH – 6.62 to 7.41 (best is 12% better than worst)

Given that, the original talk about the NB4L being ‘40%’ more fuel efficient is a bit of a generic statement – clearly things depend very much on which route is being talked about.  We don’t have the NB4L prototypes on the 38 but do have both the 73 and the 24 in the table.  With the 24 being the first NB4L route and the worst current hybrid route,  can the NB4L overcome the route’s inbuilt disadvantage and pull ahead of the B5LH sufficiently far to appear in the 7+ mpg category?  We worked out in 2010 that 7mpg would be the target, but we can now see that that would be only mid-table and not really worth the extra cost, weight or really justifying the ‘greenest bus’ tag TfL’s PR have seen fit to bestow upon it.

Indeed, things might be worse than that – look carefully at the table for Route 73’s Volvos and they come out best in class at 7.41mpg.  TfL have, of course, told everyone that they were achieving 6.1mpg, only 15% better than the 5.3mpg of diesel buses.  7.41mpg would give an improvement of 40%, the NB4L target figure.  It’s therefore entirely possible that the private bus industry has already beaten the NB4L fuel consumption target in buses costing substantially less and able to carry the required 87 passengers.  So what was the point, again, and why did TfL, in addition to telling Gwyn Topham an incorrect capacity figure, seemingly tell everyone a figure for the 73 that disagrees with their own research carried out over the previous three months?

The presentation also gives a pointer to what makes a fuel-heavy route – hills.  The 24 starts off at the Thames in Pimlico and ends up in the heights of Hampstead so is possibly the worst route to put an over-heavy bus on, if you wanted to get some good figures.  At least we know they didn’t rig the route choice to halo-up the mpg.

There are other things in the report about the rate of hybrid roll out that are also of interest – this year there’ll be 100+ more non-NB4L hybrids entering service than examples of the LardMaster itself, plus there’s still no evidence the fat bus will attract Green Bus Fund money – it’s not a certified Low Carbon vehicle.  This itself should be enough to stop any non-London UK sales, quite apart from any fuel consumption worries. 

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