Hi David,

Yes, that's broadly right. These are general terms to differential between the kind of 'old fashion' normal control vehicles and the 'new fangled' forward control vehicles needed to make the newer, longer road vehicles capable of being steered around corners. So generally, a vehicle with the steering wheel behind the front axle is 'normal' and ahead is forward. Although with a few inches it wouldn't greatly affect handing when the distance is several feet it does fundamentally change the way a vehicle steers.

So, of course, Routemasters and other half cabs are normal control. If you consider that to get in the cab you could put your right foot on the front wheel to get in, you'd be behind the front axle. This would not be the same in the 'cab over' lorries you mention, where generally you'd put your left foot on the front wheel to climb up and you'd be ahead of the axle, so forward control.

It probably becomes easier to understand if one uses the American terms to differentiate between normal and forward control. Forward control is called Cabover (ie cab over engine) the same as just about every HGV seen currently in the UK apart from the Scania N series. Normal control with a fair size bonnet stuck out the front is called conventional, which would be the fairly typical Peterbilt, Freightliner and Kenworth heavy recovery vehicles seen about.

So for PSV just about everything is/was forward control apart from the Bedford OB and LT's Guy GS class and a few others. The Northern General Tynesider and Wearsider conversions being the odd ones out.

The more recent incarnations in the PSV world like the Mercedes 6/7/8911 and Optare single deckers seem to be referred to as semi-forward control regardless of engine location.

The one oddity which springs to mind is the Dennis PAX, commonly seen as a Fremlins/Whitbread brewer's dray, which was produced in both formats.

Hi Roy,

I'm not sure that using different terms really helps if no further explanation is offered. Like David you talk about engines again but control refers to the steering, the engine placement doesn't really come into it. You can have the engine at the front, under the floor in the middle or at the back, it won't affect anything.

I've always considered the crux of the matter is the driver and as you say on a COE he is in the front, ahead of the front wheel, whereas in a Routemaster he behind, albeit very slightly! The problem, of course, is as you say, if you view this as forward control then to all intent and purpose every PSV is FC. So where then is the differential between a half cab bus and a 12 metre coach?

You do mention in your first post that they are completely different beasts so it seems odd to then see them as being of the same type. I shall continue to mull this over! All the best, Danny.

Well, I thought I'd have a look for the definition in one of the various Fundamentals of Heavy Vehicle Technology textbooks available for whatever C&G students are called these days. I have only kept the books with the various theories, formulae and equations in them, which get referred to every now and again to remind me about things like whether the 5252 comes into the 33,000 plan. It doesn't, they are two different formulae to arrive at the same answer.

As predicted by the fairly recent BBC report on major errors in GCSE and A level revision textbooks, the only reference I could find on-line has a daimetrically opposed misprint in its text!

Perhaps we'd better have a vote on it!