STANDARDS SET TO RISE
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How ready will coach builders be when new ECE and Department of Transport coach safety proposals take effect? David Wilcox considers what they mean and looks at what manufacturers have done so far to anticipate them
IT WOULD be easy for the man in the street to believe that British coaches are becoming increasingly dangerous. The media reported a spate of coach accidents earlier this summer, and the death of five St Albans schoolchildren in a French accident led to a 3,500-signature petition to Margaret Thatcher demanding roll-over protection in coaches.
The latest Department of Transport accident statistics indicate the size of the problem, although they include accidents involving buses, not just coaches. Overall, the bus and coach safety record in the Eighties is significantly better than it was in the Seventies. (See table on page 39.) RoIl-over protection is the main safety factor currently at issue, but it is by no means the only one. The DTp has seized the opportunity of putting together a "coach safety package", hung on a forthcoming standard for roof strength.
This set of proposals covers: • roof strength • seat belts • emergency exits on double-deckers • fire-retardent interior materials.
The package also contains measures to make vehicles more accessible to elderly and disabled people. These concern new step design, grab handles and handrail specifications, wheelchair restraints and step lighting_ The DTp sent out its proposals on coach safety in July to the coachbuilders, the Society of Motor Manufacturers and Traders, the Bus and Coach Council and the National Bus Company, inviting their comments by September 16 (Monday).
If all goes well the DTp believes coaches built after spring 1987 will ha to conform to new standards, althoug this date might slide back a little.
ROLL-OVER PROTECTION
AMAZINGLY, the UK Construction and Use Regulations for coaches do n( stipulate any standard for roof strengtl This is despite UK efforts pressing for an international standard for roof strength via the United Nations' Economic Commission for Europe minating in the Dibbles Bridge aster of 1975. It was there that 32 )ple died after a coach went through a ne parapet and landed on its roof. During the 11 years that the ECE has !..n looking at a roof-strength standard ; UK, Sweden, Hungary and West many have emerged as prime wers. France, though, is less than :husiastic about an international roofength standard, on the ground that atively few people die as a result of 1-over accidents_ The ECE standard is still a draft and ikely to emerge in its final form next ring. Then, it would be available for ;mber nations to adopt as a
Indatory standard in their countries. t nothing compels the countries to 31y the ECE standard.
British input into the ECE standard been a three-cornered affair, with DTp sponsoring work by Cranfield .titute of Technology and the Motor lustry Research Association (MIRA). ...,ranfield's role was to investigate I-over accidents and follow up with mlation and calculation of the rgi es going into a coach )erstructure during the accident. The anfield team came up with a set of urea for a "standard accident" that )uld cover 70 per cent of roll-overs. Mira then developed a physical test to nslate Cranfield's mathematical culations for the standard accident. At s point (about six years ago) most itish coach manufacturers took anfield's standard accident figures as a get for their body-design strengths.
it must be emphasised, was a ponsible move; there was nothing -cing them to develop stronger bodies. The major improvement was to move the point at which the roof hoops were joined to the lower half of the body. This had traditionally been at the waist rail, but it changed so that the hoops extended down to chassis level. This removed the weak point of a join from the crucial part of a body in a roll-over. Even though timber framing for coaches had largely disappeared by the early Seventies, stronger and larger sections were also used for the hoops.
SO British designs in the Eighties do offer substantially better roll-over protection than earlier bodies, even though larger glazed areas give them a frail look. Based on this, there is a widespread belief that current British coach bodies already meet the forthcoming ECE standard.
CM's findings show that they do not. Following a campaign by Hungary for greater roof strengths than catered for in Cranfield's standard accident, the draft ECE standard assumes energies going into a superstructure during roll-over that are approximately 50 per cent higher than Cranfield's figure. So although most British bodies comfortably exceed the Cranfield figure that was their original target, they fall a little short of the ECE draft standard.
The standard, which will apply to coaches under 3.8m high, is due to be finalised by next spring and the UK has already declared that it will be incorporated into our domestic Construction and Use Regulations as soon as possible. The DTp says it will then give coachbuilders at least one year to make any necessary production changes. This means that at the earliest, new coaches built and used after spring 1987 will have to conform to the ECE standard.
THE ECE DRAFT STANDARD
THE DRAFT standard works on the principle that deformation of the body in a roll-over should still leave a specific "survival space" inside. This is checked by inserting a template crossways inside the coach to represent the survival space and then rolling the vehicle over. The template is roughly in line with the centre of the outermost seats and runs up to a height of 300mm above the top of the headrest.
There are four ways of carrying out the roll-over test. First, a complete vehicle can be toppled sideways into a pit 0.8m deep. Second, a section of the coach can be toppled into the same pit. Third, a pendulum can be swung on to the roof cant rail. Finally, a mathematical calculation to prove the strength can also be acceptable.
Manufacturers could carry out the test themselves or could commission Mira to do it, in which case the cost would be several thousands of pounds.
THE HUNGARIANS — who were UK's co-sponsors for the ECE standard — wanted an immense roof strength requirement. This was because the Hungarians build roads above the level of the surrounding ground and have deep drainage ditches. Consequently a high proportion of their coach accidents are the roll-over type.
As well as pushing up the energy levels that a roof must withstand, the Hungarians also reduced the angle at which the cant rail impacts — effectively increasing the energy levels even further. If they had got their way entirely the test pit would be 1.1m deep and stepped.
DESIGNING FOR THE STANDARD
THE BEST coach in a roll-over accident is not simply one with a very rigid structure; the Mira experts say that such a body would have a tendency to continue to roll, hurling the passengers around inside. Instead, they advocate a limited, controlled amount of deformation to absorb the energy and stop the roll.
The UK is alone in Europe in having a tilt test, with single-deck coaches having to tilt to 35 deg and doubledeckers to 28 deg. This could be interpreted as working against roll-over strength since it deters a coachbuilder from putting too much weight into the roof.
That is only partially true, however. Only a stronger cant rail and roof panel adds weight at the very top of the roof. The vital stronger pillars/hoops add weight lower down, albeit at a point above the centre of gravity. Double glazing and roof-hung video monitors are more likely to be a problem than roof strength when it comes to passing the tilt test.
The shape and proportions of a body also play a part in roll-over.
A taller body may be more inclined to topple over because of its higher centre of gravity, hut once on its side it will resist going right over on to its roof.
Bonded-in glazing adds strength, but a coach's side windows arc in the shear direction, which is not a great advantage in a roll-over. But bonded side windows are less inclined to pop out in an accident and so help to keep passengers from being thrown out and trapped underneath a rolling coach.
Plaxtons says that its current Paramount range "falls a little short" of the draft ECE standard, but could be brought up to the level with the addition of roll-over bars to the structure. The company's response to the Department of Transport's coach safety package is broadly to seek more time to implement all the changes; and there are rather a lot of points to tackle.
Although by no means an insurmountable problem for Plaxtons, the company commented that it could have met the draft standard earlier "if they hadn't kept moving the target" — a reference to the influence of the Hungarians.
Another coachbuilder, Hestair Duple, is confident that its new Integral 425 passes the ECE draft standard. "We have no worries whatsoever," said a spokesman.
The company's Laser and Carribean are of the same generation as Plaxtons' Paramount and, although they fail to meet the standard, come close to it.
But Volvo's new ClOM integral has the benefit of being designed with knowledge of the latest ECE standard proposals. The model incorporates three steel roll bars and Volvo confirms that it has passed tests to the ECE standard.
The choice facing coachbuilders is either to produce a design (such as Volvo's ClOM) that has adequate strength built into it from the outset, or THERE are commercial implications attached to the ECE standard. The Bus and Coach Council says that it has no objections to the standard, provided that it is introduced by all countries so that UK manufacturers are not put at a disadvantage compared with foreign competitors.
Leyland has a particular interest with its integral Royal Tiger Doyen and is anxious that coaching does not get a had reputation. It therefore favours some form of roof strength standard, even if it is "over the top", providing that it is ruthlessly applied to all.
While the UK and most other ECE signatory countries will implement the ECE standard, two countries stand out as being rather less progressive. The French and the Spanish have adopted a sceptical attitude to a roll-over standard and may decide not to implement it.
This would pose a problem about the sale of French and Spanish bodies in the UK. Do the bodies meet the standard, and would the manufacturers or importers be prepared to conduct the necessary test just for the export markets?
SEAT BELTS
SEAT belts are not included in any ECE proposal, but they are part of the DTp's coach safety package intended for implementation in early 1987.
The proposal is for every new coach to have seat belts fitted on any forwardfacing seat that does not have a highbacked forward-facing seat immediately in front of it. In a conventional coach saloon layout this would mean the four front seats and the centre rear seat.
Single lap belts would be permissible provided that the back of the seat in front that could be hit by the passenger's head is soft or padded to a depth of 50mm.
But the Bus and Coach Council has "serious reservations" about lap seat belts, favouring some other means of retention. "The biomechanical loads imposed by a single lap belt could lead to injuries more serious than those which would have been inflicted on an unrestrained passenger," it says.
FIRE EXITS
EVERY new double-deck coach shoul have a means of escape from the uppei deck both at the front and rear. If the staircase is at one end, an emergency door at the other would be acceptable. the staircase is in the centre then emergency doors should be at both ends. All exits should have some meatof allowing passengers to reach the ground safely without jumping.
This is another part of the Department's coach safety package an nothing to do with ECE proposed standards. It is a logical development against the background of the accident in Germany this year where 18 Royal Air Force bandsmen died in a Neoplar Skyliner double-decker which caught fire.
The vehicle was a German specification Neoplan without an emergency exit on the top deck. Brith specification ones have such an exit an so this proposal should not cause problems.
SOFT TRIM FLAMMABILITY
ONCE again, this is not covered by a ECE standard, but it is something tha the UK is to introduce. New coaches must have upholstery, interior soft trii carpeting and bulkheads and floors tkconform to various British Standards I flammability.
MEASURES to make vehicles more accessible to the elderly and disabled people are also included in the Department's coach safety package, hough they do not strictly fall under safety heading.
The proposed rules apply to all ;senger vehicles with nine or more ;senger seats. The roost significant of !se is that entrance steps should be ver and deeper, with the first one no are than 300mm above the ground len the vehicle is empty.
This is widely viewed as unrealistic; ! first step at this height would give ;ufficient ground clearance and too my steps would be needed in a adern high-floor coach. Plaxtons says at the necessary changes to its step nstruction would cost at least 00,000 even possibly double or treble this.
DT PART of the Department's coach ..ety package but with a bearing on the bject are coach speeds, low driving sitions and coach seat frame strength. One frequently hears allegations of aches speeding on the motorway, but itistics show that this is perceived to a greater problem than it actually is. ie 1983 National Speed Survey found at 23 per cent of coaches exceeded the otorway speed limit, compared with per cent of lorries and 40 per cent of rs.
Launching the National Motorway fety Campaign this summer, chief perintendent David Little of the orthants Police referred to research inc in the East Midlands: "PSV ceding is not a great problem," he dared.
Nevertheless, the House of Commons insport committee safety report iblished this January says that there is strong case for coaches (and lorries) ing fitted with speed limiters once an cceptable" device has been devised. Low driving positions have also .come popular in recent years, mainly .cause they give the occupants of the ant seats a better view. Some arc wer than others; the Van Hool Astron an extreme example. But the aeinland area of West Germany's TI.JV Traffic Safety Institute has been particularly critical of low-driving positions because they restrict the driver's field of vision.
Flights of Birmingham has 18 coaches of this design, including the very low Astrons. Ken Flight says that there have been no problems whatsoever with this arrangement: "The car-like seating position encourages our drivers to keep their distance and react more like car drivers. A higher position makes drivers more inclined to drive closer and take more risks."
ALSO excluded so far from the Department of Transport's safety package is a regulation regarding the strength of coach seats and their fixings. The United Nations E.CE has been discussing this aspect for many years, but the subject has been overshadowed by the roll-over talks. The scat strength question arose partly because of a British accident where the scat frames sheared off.
The UK is in favour of seats having to withstand a force of 10g, whereas the French say that seat strength is not a problem in their experience and so favour a 5g level. The ECE countries are due to meet in Hungary three weeks from now to finalise the seat strength standard. What could emerge might be a dual standard — 5g and lOg — with countries able to choose which they prefer!
Meeting the lOg figure should not be a problem for British manufacturers. Hestair Duple has recently carried out sled tests at Mira on the seats in the Integral 425, achieving 15g for the fixed seats and 11.5g for the recliners.
If the seat strength standard is finalised before too long the DTp may add it to the coach safety package.
The Department is having to be a little cagey about the implementation date for the coach safety package because of a shortage of manpower in its vehicle standards engineering and drafting sections. Coachbuilders are also likely to seek more time to make the production changes and so spring 1986 for introduction and spring 1987 for implementation are the earliest possible dates.
If Britain had chosen to go it alone instead of spending a decade seeking an international roof strength standard, progress would have been very much quicker.