Friday, December 24, 2004

The Case Against SUVs Part 1

I've been thinking lately about the proliferation of 4WD vehicles on the road over the past decade and have decided that it must stop, for the sake of the environment and people. Before I get too far into the rant, I'll mention that there are some people who do actually utilise the full scope of features of these vehicles, and actually need them. The real targets of this rant are the purchasers and therefore contributors to the world's problems.
People must stop buying these vehicles. Here's why (this applies to both 'real' 4WDs and the urban variety (which are even worse).
First of all I'll describe the features of an off-roader and a soft-roader, then I'll explain why they are bad. Features found on all vehicles in this class are: 4WD drivetrain, classic 2 box body design, large, heavy wheels and tyres, many run on diesel, have a high kerb weight (except for the very small variety (like the Suzuki Samurai which are largely exempt from this rant because most of the bad features are cancelled out by their light weight and tiny engine)).
The 4WD drivetrain on SUVs and their relatives are either full-time 4WD or sometime 4WD. This is bad for a couple of reasons. Whether full-time or part-time, 4WD systems are heavy. Such drivetrains have many more moving parts and therefore have much more of what is called 'drivetrain losses'. That means that for every revolution of the drive wheels there is less power getting to the ground than on a similarly powered 2WD vehicle because of additional friction and other energy losses from the extra drive shafts, differentials etc. Simply put, if 2 identical vehicles, one 2WD and one 4WD, drive the same distance, in the same conditions and with every other variable identical, the 2WD vehicle will use less fuel. Multiply the extra fuel used by 1/4 of a billion or more and you'll have some idea of how much extra fuel is being wasted world-wide. Also, if you add the extra weight of the 4WD drivetrain you'll increase the fuel consumption again.
People argue about the benefits of 4WD, from handling and grip versus weight and other such things. The grip is a given, but the handling advantage of 4WD has been made largely redundant on the road due to the development of stability control systems. All Wheel Drive on a road car is all well and good, but soft-roaders usually have large tyres that negate any advantages by raising the centre of gravity of the vehicle (yes they can roll right over motorway median barriers with no trouble at all) and providing less than crisp steering. Conventional off-road vehicles also have a lot of ground clearance for traversing rough terrain, but many soft-roaders have little to no more clearance than many road cars, and do not have underbody protection, thus rendering them little better than a normal road car without the benefits.
Keep checking for part 2- Who is safe? Really?

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