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'Camber' vs 'Cross-fall/super-elevation/banking'.

17648 Views 3 Replies 2 Participants Last post by  Intergrali
Quote: Do you mean "bank" or "camber"?

I've noticed this confusion several times on other sites and spent an hour or two before Christmas knocking out a simplified explanation.
I decided it was high time to get it lodged here, in SlotForum, where it stands a much better chance of being preserved for the future.
Here we go . . .

From 40 years in the business of making roads, R J Maxwell I know that these two terms are among the most apt to confuse nearly everyone, even road engineers! But they do NOT mean the same thing and neither one is just a variation on the other. They are quite distinctly different.

'Camber' really means 'arch' or a convex section, domed. Like the letter D lying on its back, flat side down. Persistent misuse and misunderstanding of the word has allowed its meaning to degenerate into ambiguity, where people think 'camber' is more or less the same as banking. Even some dictionaries incorporate this ambiguity and they are plain wrong.
It isn't.

In road engineering terminology, 'camber' is specifically confined to the transverse section of a road where BOTH the two outside edges are lower than a line lying somewhere between those edges. The road edges may or may not be at the same height as each other but BOTH are lower than that high line between them. This situation NEVER occurs on a slot racing track, except by accidental warping and one would be swift to try to remove it if it did occur!

That high line is usually, but not always, the centre of the road.
In a two-lane, bi-directional single carriageway, (your average 'B' road) the high line should always be in the centre. But, for instance, in a three-lane version, the high line should run along a line delineating two of the three lanes so as not to site the high line in the centre of one lane (making it an absolute bugger to drive on!). The one and ONLY reason for incorporating camber is to encourage the lateral runoff of rainwater. Without it, on a flat road, the surface water would tend to pool on the carriageway and constitute a serious hazard for cars. So, let's be clear - road camber has absolutely NOTHING to do with facilitating the negotiation of curves! It is purely fortuitous that, when a car is on the inside of a cambered curve, it does (by pure chance) endow this benefit. But conversely, when you find yourself travelling a little too fast on the outer curve of a cambered road, you will feel that adverse camber trying to throw you off! Yes it IS most definitely unsafe in that situation and hence such roads are often speed-limited, at least on the curvy sections.

Camber works well on straight sections, where the rainwater quickly runs off to drainage at either side, although overtaking is still a little hazardous because of the unavoidable change in the car's attitude when shifting from lane to lane. For this reason, the degree of camber or slope is strictly limited by law and such roads often carry a lower speed limit.
Camber is also cheap to construct.

The MUCH preferred alternative to camber is 'cross-fall', where the profile of the road is designed to drain the water right from one side of the road to the other, across its full width, without being impeded or prevented by a high point between the edges. 'STRAIGHT cross-fall' is the ideal, where the angle of fall remains the same across the full road width (but see note later). The road profile is carefully designed to fall towards the INside of every curve, thus also enhancing the cornering power of vehicles. Unfortunately, this means that the slope of the cross-fall MUST be reversed in direction when the road curves the other way! Frequently alternating curves demand much more careful profile design work and often very substantially increased construction expense (depending on the lie of the existing ground).

On high speed roads, the design engineer will keep the necessary degree or angle of cross-fall very low on the straight sections, aiming for a balance that encourages the flow of surface water off the road without unduly upsetting the straight line road holding of the cars travelling along it. However, on curves, he will often aim to increase the angle of the cross-fall, in order to enhance the cars' cornering ability. Where this cross-fall is very high, it is usually termed 'super-elevation', which involves a great deal of construction 'fill' on the outside of the curve in order to raise the outer edge higher still. Really heavy super-elevation results in what many people call 'banking'!

So there you have it, if in somewhat simplified terms.
A clear distinction between 'camber' and 'cross-fall/super-elevation/banking'.
The latter three ARE variants of each other but 'camber' is a distinctly separate concept.
NOTE: For all sorts of complex (and good) reasons, the angle of cross-fall across the road is very frequently NOT constant as has been assumed in the simplified situations described above and this inconstancy lies at the root of the confused use of 'camber'!

If it is any consolation, many road engineers often use the wrong terminology even today and, if THEY can't get it right, it is hardly surprising that the confusion is perpetuated. It is a never-ending source of amazement to me that, in spite of this, most roads actually do fulfil their design intentions!

Something different to think about on your boring drive to work!
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camber, a few degrees off from horizontal,

Bank, very visible with the outer edge very high!

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