High Speed Double Deckker?

Question

I do not have a degree in Rocket science but surely it is obvious if you have a bus with a couple of tons of Human ballast 10 feet or so above road level it will be unstable and turn over if forced to swerve, and if French ones turn over then identical English ones will too. Have I missed something or is it Stagecoach management who have missed the obvious.

Answer 1

Judging by my own experience of heavy and high-sided double-deck vehicles in the trucking industry, I was surprised to learn that a double-deck coach had turned over; even allowing for the possibility of excessive speed and driver inattention.

Naturally, the investigation into the specific circumstances of the accident may reveal the contributory causes, and thus, any comments I care to make may have little or no relevance to the facts of the case.

However, without wanting to pre-judge the situation, I will suggest a few possible causes.

The first cause may be excessive speed, but this alone would not turn a vehicle over on a bend. However, IF there was a swerve one-way and then the other, the sideways momentum is greatly increased, as the body rolls first to one side, then back: helped by the springs and anti-roll bars which uncompress. Nevertheless, I would have thought that the vehicle would have lost grip before turning over, and my first reaction would be to suspect some other contributory factor.

Other factors which could play a part, are a defective rear-steer mechanism, which I would have thought was designed to lock-out at speeds over 30mph. If it failed to do this, not only would the vehicle want to turn more sharply than intended, but it would be very difficult to keep stable in a straight-line, and even more difficult to control if the vehicle lost grip and slid.

Nowadays, many motorways in the UK have deep ruts in the slow lanes, slip-roads and link-roads, and that can also be very de-stabilising. Usually, this affects empty trucks, which can weave about as they "tram-line" in the ruts; much to the alarm of fellow road-users. Again, it would surprise me if this was a contributory factor in a roll-over accident.

2 tons of passengers on a top-deck is nothing, compared to the overall weight of the laden vehicle and the very low centre of gravity. Even a coach with a full top-deck and an empty bottom deck, should be entirely stable, even though it would roll around a little more than normal.

Another possible contributory factor could be punctured or soft tyres, but again, this would not normally result in a disastrous roll-over accident.

That leaves, to my mind, two possible alternative theories.

The first is the possible presence of high-wind, such as has been seen in the UK in the past few weeks. I recently had a double-deck trailer up off the road on one side, but that took a gust of wind probably in the order of 80mph. It was a scarey moment, but the vehicle didn't roll over nonetheless. However, combine a swerve with a gust of wind, and that could spell disaster.

The only other possible cause that I can think of, is when a vehicle is rolling and perhaps sliding also, and hits a kerb or other raised portion of road. It may be the case that the link-road being used, had a split-level road merge, with a raised banking separating them. If a vehicle hit one of these banks whilst already leaning over, it is conceivable that it could flip onto its side.

My own instinct suggests the last possibility, but as I say, we will have to await the outcome of the enquiry and any subsequent court-case.

Naturally, such events are very sad and mercifully very rare.

Answer 2

First of all the double deckers aren't "high speed". They can only legally do 70MPH and are restricted to that speed, compared with the rest of the vehicles on the motorway that's fairly slow.
It wasn't Stagecoach's coach, it belonged to National Express.
Trucks that can operate at 44 tonnes have a lot more mass higher up, but aren't famed for falling over.
The centre of gravity of the double decker is at a point just above the axles as the engine, gearbox, fuel tank etc are all below the bottom deck.
Every vehicle will have a speed at which the will flip when a kerb is hit and if the driver over-reacts.
Just think, when was the last time it happened in the country?

Answer 3

Pity, because a rocket scientist may have noticed that we've had double-decker buses swerving around, and between, many of our major towns and cities for at least 40 years!

The most common accident reported is when one of these beasts loses the top deck whilst trying to travel beneath a low bridge.

This is the first time I've heard of a double-decker vehicle toppling over, in the UK, but, as has been mentioned, most vehicles can be crashed in this way, if driven beyond their limits.

Answer 4

The details of the coach have been posted that with an empty bottom deck and a full top it can lean to 28* without tipping over although this is a stationary coach i would think with the centre of gravity being so low on a coach they are not easy to tip. However this doesnt account for road camber , weather , tyre pressures , speed. The driver has been arrested , its only fair to wait on the outcome of the inquiry.

Answer 5

A bus can go at a 45% angle before it turns over, this includes a double decker.

Answer 6

a bus never goes faster than 20mphhere in england so it wont tip over unlike the french drivers like to get where there going faster they will probably do 50mph round a sharp corner which will make it turn over. have you ever been in a bus which turned over?

Answer 7

Having read musonic's reply i find my self in broad agreement allowing for unknown factors , the possibilities are quite feasible. AS he says though we should await the results of the various investigations before we jump to any conclusions