While I’ve been away I’ve been researching bus weights. Well, someone has to.  As part of this I put in a Freedom of Information request to TfL asking:

1) The delivery and first service date for each of the nine New Bus for London prototypes and pre-production vehicles ordered for London (LT1-LT9)

2) The official kerb weight for each of the nine New Bus for London prototypes and pre-production vehicles ordered for London

3) The placarded capacity (upstairs seating/downstairs seating/downstairs standing) for each of the nine New Bus for London prototypes and pre-production vehicles ordered for London

They came back, for TfL, commendably fast but there’s still an open question as I shall now explain.

The basic rules of bus weights are that, for a two axle vehicle like the NB4L, the maximum weight, fully loaded with passengers, crew, fuel etc. cannot exceed 18000kg.  That’s the ‘gross weight’ and is set in the 1986 Regulations as:

The weight specified in column (5) of Part I of Schedule 11 in the item which is appropriate having regard to columns (2), (3) and (4) in that Part, the laden weight of the bus being calculated in the manner described in regulation 78(3) to (5)

Which is as clear as mud, but it turns out everyone builds double deckers to a maximum gross vehicle weight (GVW) of 18000kg.  Bear that in mind.  Now, in order to work out our capacity, we need to know the bus weight empty, which is written on the side, but to be sure I asked TfL this and they replied that it is 12650kg, which matches my own observations of two of them.

Now, that’s quite a heavy bus, my observations of other vehicles came up with a normal range for a modern London hybrid double decker of between 11900kg for the ADL Enviro400H and 12300kg for the longer, heavier Wright-bodied Volvo B5LH.  Individual fleets vary a bit, but that’s the range, so Boris’s ‘sleeker’ bus is about 350kg heavier than the heaviest regular hybrid and a whole three quarters of a tonne more than the commonest current hybrid, which is also considerably shorter.  It turns out that building a long bus with two staircases has a weight penalty. Who knew?

The crunch is that every kg you put on the empty bus is a kg off the payload, given our maximum 18000kg limit.  The current regulations known as Regulation 107, adopted in 2009 and in force for new vehicles since October 2010 stipulate 68kg allowed per passenger.  The older regulations specified 65kg.  For those two weights our 12650kg bus allows us:

  •  78 passengers at 68kg
  • 82 passengers at 65kg

Given that the bus was clearly specified to carry 87 passengers we’re in trouble here and TfL’s response admits there’s a problem:

It should be noted that the current vehicles on route 38 are prototypes, subject to modification, following a period of evaluation. They currently have a slightly lower capacity of around 83 passengers but once design refinements are made to the first generation of production vehicles, this will rise to the anticipated number of 87.

‘around 83′ seems to mean ’82, if we use a standard passenger weight that was superseded two years ago’.  TfL appear to be stretching things by using 65kg, as manufacturers are already working on 68kg elsewhere, such as the new  (and rather hefty, if truth be told) Volvo B9TL/MCV launched this year, which weighs 12375kg and has a capacity of 63 seated/19 standing, which at 68kg brings it in just under spec at 17951kg.

The question has to be asked, therefore, why Boris’s pet bus gets away with using an outdated passenger weight under which, at design capacity, it would have a GVW of 12650+65*87=18305kg.  If we go with the current standard, and they’re going to have to argue quite carefully that the production vehicle is not subject to this, it’s even worse at 12650+68*87=18566kg.  That’s more than half a tonne to lose, which is a fair bit of ‘refinement’ on a bus which TfL are expecting to buy 600 of almost immediately.

Actually it might be even worse than that – the pointless standing-around-person, who won’t check or sell tickets but will cost us £40m a year in subsidy presumably counts as another 68kg, which you have to save from somewhere otherwise you can’t have the open platform.  Call it a round 650kg then, or about 5% of the original pre-production bus that needs to be trimmed off.  It’ll be interesting to see how they manage that given that Heatherwick Studios were already aware of the need to lighten it to meet the fuel economy target:

Having set the environmental target of using 40% less fossil fuel than existing buses, the team developed a hybrid vehicle, powered by both electricity and diesel, seeking to make it as lightweight as possible.

Could the fuel economy also be taking a hit from the weight, given that it’s supposed to be 15% more efficient than the Enviro400H, which weighs 6% less?  A comment thread on Omnibuses suggests it might be, plus revealing that Leon Daniels, the bus nut Peter Hendy brought in to bugger up the bus network for ordinary people, has essentially admitted online that the buses are overweight due to using heavier materials than planned. Presumably that’s due to the election-based timetable.

P.S. I went on an original RML Routemaster the other day.  That has an empty weight of 7874kg and a capacity of 72 seated/5 standing or, in other words, weighs about the same when full as Boris’s lardbus does empty.  Any examples of anyone pretending the Lardbus for London is ‘light’ will be gratefully received.

P.P.S. TfL’s Mike Weston’s updated his hybrid bus PDF, now up to May 2012.  Includes fuel economy statistics (claiming 11.6 for the NB4L) and also a diagram of the NB4L from 2010 which indicates that both decks were designed to EC Regulation 107, which presumably implies it should have used 68kg and therefore have a legal capacity of less than TfL told me in the FoI.  Hmph.

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