This may seem strange but, when I’m out in my car, I’m driving with a self-imposed speed limit, lower than the national maximum. This involves sticking to 50mph on roads where 60 or 70 are allowed. Generally I am pretty good at driving up to the speed limit at all times (bar a few mistakes). So far I’ve never had a speeding ticket – although I’m wary of putting that bit of personal info out there as it will guarantee getting caught by a speed camera in an unguarded moment very soon. So why impose a reduction in my personal speed limit?
The simple answer to that question is that I want to drive ‘greener’. I’ve read that reducing speed from 70 to 50mph can reduce petrol consumption by around 15%. For those who have invested in electric cars, the same change in speed can increase the battery range by up to 70 miles, depending on the model and battery size. In either case this means reduced energy costs and, more importantly for me, less carbon dioxide produced through burning fossil fuels.
Imposing the lower speed limit on myself involves certain exceptions. For example, if I’m on a single carriageway with cars behind me, I will drive at 60mph as the 50mph imposition is meant to be on me and not all other road users. Also, I’ll occasionally have to bust it in order to overtake vehicles that are doing, say 49mph. I don’t want to become one of those drivers who pull out into the faster lane in order to overtake a vehicle by driving 1mph faster and taking an absolute age over it!
There are a couple of other environmental factors that can be improved with ‘driving greener’. One is the amount of dust from the wearing down of brake pads; the other being the plastic particles dispersed in the environment – especially in rivers and lakes – by the wearing down of tyres.
The former can be tackled by reducing braking force and the amount of braking required. Please excuse me if the physics teacher in me pops out for a moment, pointing out that braking force is used to transfer away the kinetic energy (movement) of a car and bringing it to a halt. The greater the speed of the car, the greater the kinetic energy In fact if you double your speed, your kinetic energy quadruples as it depends on the speed squared. (ke = 1/2 mv2 anyone?!?). The upshot of this is that by driving at 50mph instead of 70, braking force is almost halved which should reduce brake pad wear and tear significantly.
As for tyre particulates, one way of reducing them is to drive gently – which means less rapid acceleration and slower manoeuvres like taking bends and corners. Lower speeds should help contribute to this.
All in all, I suppose the best way to drive ‘greener’ is not to drive at all and cycle, walk or take public transport but, when driving is required, I’ll try my self-imposed speed limit and let you know how I get on.