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Are you really safer in a bigger car?

In the event of a crash, are your chances of survival better in a bigger car? Ian Law sounds off.

Published May 2, 2011
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There is a large segment of our driving population that believes a larger vehicle will keep them safer on our roads. In reality, this is not true at all. There are too many variables in a car crash to be able to simplify that equation.

Some motorists are buying SUVs, pickup trucks and mini vans in the hopes that the added size will protect them in a crash. They believe that extra metal surrounding them will keep them safe in a cocoon of steel, that the added mass will help them survive a catastrophic collision and that an extra metre of height will help them see farther down the road.

The only advantage these behemoths do provide is the ability to see farther down the road from their higher seating position. As important as vision is to safe driving, it does the driver and occupants little good if the driver is not using proper vision training. Unfortunately, most drivers are not taught vision training techniques.

Related: What’s with all the gas guzzlers, anyway?

In some collisions, the added mass can be of help, but only if the vehicle is colliding with an object of smaller mass and only if that larger vehicle does not roll over as a result of the collision. Large vehicles such as SUVs and pickup trucks have a higher centre of gravity, which increases the likelihood of the vehicle rolling over during a collision. This can lead to severe head injuries to the occupants. These vehicles are also more prone to rolling over in single vehicle crashes.

The extra mass can also be detrimental to safety. The more mass involved in a collision, the more energy that needs to be dissipated. If a large SUV hits a wall or truck, much more energy is involved in the crash than if a smaller vehicle hit the same wall or truck (if the velocity is the same). Therefore, you are not necessarily safer in a larger vehicle, and if the speeds are significant the results can be fatal.

Survivability comes down to the design of the vehicles’ crumple zones and passenger safety cell. The safest vehicles will have a crumple zone designed to absorb the impact (dissipate all that energy by deformation) by crushing in a designed way to gradually slow the vehicle. The passenger safety zone will be designed to sustain the impact without deforming or allowing the passengers to impact any part of the vehicle. This is a technology that Volvo has worked on for more than 40 years. Volvo did not build large vehicles to increase its safety record, they just built better designed vehicles.

The added mass of an SUV also works against safety when it comes down to trying to avoid a collision.

As you recall from your high school physics class, any object in motion is subject to inertia. The greater the mass, the more energy is required to slow that object or change its direction. Therefore, the heavier the vehicle, the longer its stopping distances will be and the less agility it will have to avoid collisions.

With the exception of BMW and Mercedes Benz, which are building SUVs with massive and effective brakes, most SUVs, pick up trucks and minivans will take longer to stop than most cars. Even the exceptional engineering of these automotive leaders cannot overcome the effect that the extra mass has on handling. These SUVs still do not handle as well as their smaller brethren.

As motorists, we need to be thinking along different lines here. The ‘bigger is better’ attitude is based on surviving a crash. We should all be approaching safety on our roads by thinking about avoiding crashes and collisions. In other words, “Let’s avoid collisions, not hope to survive them.”

Motorists who buy large vehicles for safety are only hoping to survive a crash. There are too many variables involved in any crash to predict whether you will survive it or not. If you have your head turned at the wrong angle at the moment of impact, you can fracture your neck no matter what vehicle you are driving. We are always better off avoiding any impact.

If I was driving along a two-lane road with two transport trucks approaching and one pulled out in front of me into my lane to pass the other, I would much rather be in a Mazda Miata than in any large SUV. In the Miata, my chances of avoiding the collision are very good, where in the SUV, I would be a hood ornament on the front of the oncoming semi. SUVs and pickup trucks lack the agility for emergency evasive manoeuvres.

Along with the collision avoidance aspect of all this, there is another issue. Larger vehicles block the vision of drivers in smaller vehicles. Vision is a major component of safe driving and being able to see farther up the road is vital. Larger vehicles blocking that vision can result in drivers having to rely on reacting to the vehicle directly in front of them. When a motorist may want to make a turn into an intersection, their vision to check for oncoming traffic can be blocked by the larger vehicle. This impairment of vision is a safety threat to all smaller vehicle drivers and is a great concern.

Does size matter? Yes, but not in the way you think it does. Before you purchase a large vehicle in the belief that it is safer, give these points some consideration.