Does bigger mean safer?

By Paul Hudson for CNN

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LONDON, England (CNN) -- Many people see them as conspicuous consumption gone mad, the cause of climate change due to high emissions, but are Sports Utility Vehicles (SUV) and people-carriers simply getting bad press?

A backlash against the hordes of these generally large and therefore highly visible vehicles on our roads -- and particularly our urban centers -- is happening. The most recent case was in London, in the Borough of Richmond upon Thames, which has proposed much higher charges for residents' parking permits for owners of so-called "gas-guzzlers."

There's also envy at work, with many people seeing the vehicles as show-off toys for the wealthy, and there's no disputing that some of these vehicles are extremely expensive and have large-capacity V8 engines which use a lot of fuel.

But how about the safety implications? It has long been a truism that, in the event of a road crash, the more metal around you the better.

Recent advances in crash structure engineering, with the aid of high-powered computer simulations and stress tests, have made smaller vehicles much safer for occupants. So who needs a four-wheel drive (4x4) any more?

Well, according to figures from the UK's Transport Research Laboratory (TRL), which has been involved in improving road safety for more than 35 years, 4x4s and MPVs are safer for drivers and their passengers when it comes to collisions with roadside barriers. This contradicts recent media coverage which showed that this type of vehicle was not a good place to be in the event of a crash.

Its independent report finds that occupants of these vehicles are less likely to be killed or seriously injured in a two-vehicle road traffic accident than those in other types of car. What's more, those occupants are also more likely to avoid injury altogether, and drivers of these vehicles are five times less likely to hit a crash barrier than those in other types of car.

Also, according to UK road data, SUVs are "under-represented in accidents on unclassified roads." But, as ever, that might be because owners of larger vehicles use this type of road less frequently.

TRL's research shows that only two per cent of strikes against roadside barriers involve 4x4s and MPVs, although this type of vehicle accounts for about a tenth of all cars on Britain's roads. That means the drivers of 4x4s and MPVs are five times less likely to be involved in this type of collision.

The Society of Motor manufacturers and Traders, the UK's car-trade organization, claimed that these findings are most likely due to this type of vehicle more likely to have the latest electronic accident-avoidance systems fitted as standard, such as ESP (Electronic Stability Program) to prevent skidding and loss of control. It added that the huge investment by manufacturers in active safety systems like ESP, as well as anti-rollover technology, assisted braking and lane departure warning systems, is saving lives every day.

And why do manufacturers spend such huge sums developing safety? While it's obvious that they don't want their customers to be injured, these days safety sells as much as -- if not more than -- traditional measures such as top speed, acceleration times and economy.

The EuroNCAP crash test program has become the accepted measure for passenger car crashworthiness, and five stars virtually guarantees sale success. It has grown so important that every manufacturer craves a good score -- witness Renault which, thanks to a string of top-grade EuroNCAP ratings of five stars for occupant protection, is now viewed by the general public as a maker of "safe" cars.

Conversely, a poor score can ruin a model's sales prospects, or even hasten its demise. A lowly one-star score for the Rover Metro/100-series supermini led to scare stories in the media and buyers voted with their feet, shunning the model. Poor sales meant that it eventually was dropped from sale and went out of production. There was a similar scare with the Chrysler Voyager people-carrier, ironically in the class that the TRL research found was safer in the event of a collision with a roadside barrier.

By law, all new car models must pass certain safety tests before they are sold, but legislation provides a minimum statutory standard. EuroNCAP testing aims to provide car buyers with independent information about a car's safety. The organization only makes comparisons within size categories.

The EuroNCAP program involves a series of trials designed to replicate the most common types of road traffic accident, to see how each contender performs relative to others. The first test is a head-on crash into a deformable barrier at 65km/h, a speed slightly higher than that required for European homologation, to replicate the type of crash that leads to the most deaths and serious injuries.

Readings taken from dummies gauge how well the car's body stands up to impact and, therefore, how a human occupant might fare in a similar collision.

There is also an optional second test, a side-on impact into a pole which measures a car's protection from being hit at an angle of 90 degrees.

Each car must undergo pedestrian impact tests, designed to show how "pedestrian-friendly" they are if they hit an adult or child (involving separate tests) at 40 km/h.

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