Speed-bump, road hump, speed ramp or sleeping policemen. Let’s face it by any name they are the bane of urban driving (unless of course you make your living selling replacement shock absorbers). They’re a hassle, damage cars and cause urbanites to drive otherwise unnecessary 4x4s (in my experience anyway). Yes, average speeds are reduced, but so is your attention of what’s up ahead as you’re trying not to clout your exhaust on that unnecessary piece of road calming. Other complaints made against them are that they slow down emergency services (endangering lives), they are particularly unhealthy for people with back or neck pain and create noise for local residents.

Speed Humps

Speed Humps

But I can add another one, that they’re giving the poor Polar Bears an early bath. Yup, that speed bump round the corner on Mornington Close is directly responsible for the increasing popularity of bear-centric swimming lessons at the North Pole. So let me tell you how….

The AA (Automobile Association) did a bit of research on fuel consumption for cars at the Millbrook Proving Ground and found that a typical mid-size car running at a constant 30 mph did 58 mpg. However a car slowing down and speeding up for speed bumps only did 31 mpg. Put that into carbon figures* for a petrol car** and you get 113 g/km of CO2 at a constant 30mph, or 211 g/km over speed bumps. So a kilometer of road with speed bumps creates an extra 0.1kg of CO2 for every single car that travels it.

For argument’s sake, lets say this km of road has on a average a car going each way down it every minute during the day and night***. In a year, that means a single stretch of road creates an extra 103 tonnes of unnecessary CO2 per year. We’re making estimates here, but if that km of road has 10 of the UK’s estimated 100,000 speed humps, then speed bumps in Britain are responsible for a colossal 1.03 million tonnes of CO2 per year. That’s about the same as the total carbon footprint of the 830,000 residents of Fiji, or almost twice that of Greenland. Ouch.



You can console yourself that as a UK taxpayer, based on the estimate that 50 standard humps on three or four connecting residential streets costs about £150,000. So the UK speed hump population cost us £300 million pounds. Which is about what Newcastle United would cost you if you wondered up to St James’ Park with a really big chequebook this morning.

*Clear research

** A diesel car is actually worse with 128 v 240 g/km

*** More in the day and less at night of course

More information here.

You want to be environmentally conscious right? Reduce your carbon footprint, do the right thing and save the polar bears? But in the back of your mind, you’ve always wanted that sports car you could never afford. That present you’d always promised yourself. But sports cars aren’t exactly the environment’s best friend are they? Can you really have the best of both worlds?

A Green Porsche

A Green Porsche

Well the answer is yes, and to demonstrate how I’m going to use two flatmates, Vegetarian Sam and Capitalist Rufus. They both work in central London, live in the suburbs and both require non-public transport at weekends, holiday in the same place and have very similar lifestyles. The only difference between them is the transport choices they make.

Sam takes the train (60.2g/km*) and bus (67.8g/km*) to work everyday. He has a 6 year old Ford Focus 1.8 TDCi (145 g/km*) which he drives at weekends.

Rufus rides a scooter (Vespa 50cc @ 72g/km**) to work and at weekends and refuses to use public transport. He (cue much teeth-sucking disapproval) also has a Porsche Boxster (227 g/km* for the weekends). And let’s try not to hate him just because he has a Porsche. Let’s pretend he uses it at the weekends to take old people to the seaside.

Sam and Rufus work in the same office everyday do exactly the same distance each year, so how can Rufus, the Porsche-driving capitalist scum be greener than his vegetarian, flip-flop wearing flatmate?

The Commute:

Sam and Rufus both travel from Clapham Junction to Liverpool Street every day. Sam takes the train to Waterloo (6.3km = 0.76 kg CO2) then the bus for (4.8 km = 0.65 kg CO2) giving a total of 1.41 kg per return journey.

Rufus goes direct door to door on his Vespa which is 8.9 km (compared to Sam’s 11.1km), producing 1.28 kg of CO2 for his return journey.

The Weekend:

Sam and Rufus both travel at the weekends, and they each rack up 4,000 miles per year driving in some form. Sam does all his miles in his Focus (934kg of CO2), whereas Rufus does 1,500 of these in his beloved Porsche taking old people to the seaside (548 kg of CO2), while the other 2,500 he does on his trusty scooter (290 kg of CO2), a grand total of 838kg.

The Total:

So where does that leave us?

CO2 Footprint Commute*** Weekends Total

Sam 310 kg 934 kg 1,244 kg

Rufus 282 kg 838 kg 1,120 kg

So vegetarian Sam takes public transport to work every day, drives an efficient diesel car but still has a 10% bigger carbon footprint than capitalist Rufus and his petrol guzzling Porsche even though they travel exactly the same distance.

So can you be green and drive a Porsche? Looks like it. It just goes to show that it’s not quite as simple as it seems to condone sports cars….


* http://www.defra.gov.uk/environment/climatechange/uk/carbonoffset/codeofpractice.htm / VCA car fuel data.

** Clear analysis

*** 220 days a year

Sports cars. With the exception of the real die-hard lentil sandal wearing environ-mentalists, most people love the idea of a sports car. But admit that at an Islington dinner party and it’s about as PC as claiming you’re Osama Bin Laden’s tennis partner. So can you really have a green sports car?

A blue green car

A blue green car

Arguably the greatest ever car designer was a chap called Colin Chapman who founded Lotus. His most famous quote on making fast cars was “Simplify and add lightness”. He also said “Any car which holds together for a whole race is too heavy”, but let’s not worry about that right now. Chapman believed that to make a car faster you make it lighter. If a car is lighter, then you need smaller brakes, a smaller engine, smaller tyres and so on to get the same level of performance. Which means the car is lighter still, creating a rather nice virtuous circle. You also save fuel costs, for example reducing the weight of a car by 100kg will save you about 900 litres of fuel over it’s lifetime*. That’s about £1,200 at today’s fuel prices. Then again you could also argue that by cutting down on the burgers and losing 10 kg, that would save you £120!

Chapman sadly died in 1982, but I suspect he’s turning in his grave as he sees how bloated and overweight cars have become. What’s frightening is the statistic that although the average weight of a car in Europe is around 1,200 kg, in the US it is 2,000 kg. In the last 25 years since his death, the average weight of cars has increased by 60% in some classes**. And cars on average are getting heavier by 16kg every year***.

Very interesting, but what relevance does this have to CO2 or that lovely sports car you want? Well, to get a car to any speed you need to add energy. 0.5 x the mass of the car x the speed**** (squared) to be exact. Halve the weight of the car, and you halve the energy needed, and halve the fuel required to get to that speed, and the amount of CO2 that gets produced as well.

The same is true with speed as well, except the amount of energy required is squared. So to get 100mph requires 4 times the energy to get to 50mph. Admittedly once you’re at speed, then the aerodynamics play more of a part in how much fuel is burnt (and CO2 that is produced), but lets concentrate on the weight for now.

The trouble with this kinetic energy is that when you slow down it’s changed into heat in the brakes, and it’s gone. This is where regenerative braking comes in. Hybrids and Electric cars can use their motors as generators and save this energy to use again. But they’re still thin on the ground, and unless you have £100,000 for a Tesla Roadster (www.teslamotors.com) you’re out of luck if you want a sports car.

So where does that leave us? Well, funnily enough where we started with Lotus. Generally 2 seater sports cars tend to weigh in between 1,200 and 1,500kg*****. A Lotus Elise in 1996 weighed just 720kg. Even now with airbags, safety equipment and crumple zones it weighs about 900kg. That means it needs a smaller engine, brakes and so on to give the same performance. And that also means less CO2.

As an example, a £140,000 Ferrari 430 will hit 60mph in 4 seconds and produce 420 g/km of CO2. A £32,000 Lotus Elise SC will hit 60 in 4.4 seconds and produce 202 g/km. Which is less than a bog standard Volvo estate.

So there you go. If you want to go green, but still want a sports car, then buy a Lotus.

* http://www.engineeringtalk.com/news/jsr/jsr103.html

** Source: SMMT

*** http://news.bbc.co.uk/1/hi/sci/tech/4922614.stm

**** Speed in metres per second

*****eg: Porsche 911 – 1,400kg, Ferrari 430 – 1,450kg, Porsche Boxster 1,420 kg, Honda S2000 1,274kg

Source: Clear research

A Toyota Prius looking smug yesterday

A Toyota Prius looking smug yesterday

Hollywood loves the Toyota Prius for the green image it purveys to celebrities who have a carbon footprint several times that of the average citizen. Middle England loves the Toyota Prius because over a dinner party they can tell their neighbours they drive a hybrid car. I even like the Toyota Prius because it has raised awareness of hybrid technologies to the world, and brought them into the public consciousness. But is it as green as Toyota claim?

Well, the official CO2 figure for the Prius is 104 g/km, which is equivalent to 62.8 mpg (although Toyota actually claim 65.7 – someone in Japan has their maths wrong there). Now DEFRA in their guidelines to the carbon offsetting quality standard (which is soon to be released) says that reported g/km “factors must be uplifted by 15% to take into account ‘real-world’ driving conditions”. This is not Prius-specific, but does admit that even the government doesn’t believe the CO2 figures they use to tax us on.

With this uplift, the Prius would now be at 119.6g/km (54.6 mpg) which on the face of it seems more reasonable. In independent tests the Toyota has also failed to live up to its claimed efficiency, with What Car (1) recording 52mpg, The Sunday Times (2) recorded 48.1 mpg on a long journey and owners typically reporting between 53 & 54mpg. This gives us a worst of 48.1mpg and a best of 54mpg. Translating that into CO2, that’s 121 to 136 g/km of CO2. So not bad, but still 16-31% higher than Toyota claim (104 g/km) and very misleading.

It’s also worth remembering that a hybrid engine is only beneficial for lots of stop start driving. Running at constant speed there is no benefit over a normal engine, and in fact a disadvantage because you are carrying the extra weight of unused batteries and motor. It’s also worth noting that fuel consumption (and hence CO2) is all about your driving style and not what you drive. 91mpg was achieved by a chap called Will from Warwick Uni (3) in a VW polo Bluemotion, in excess of the claimed 74.3mpg and that included traffic on the M25. A Prius will also cost you more than an equivalent non-hybrid car, and the extra money you spend will take a long time to recoup (if ever). And if you were thinking about buying one to replace your old car, remember that means that somewhere another vehicle needs to be manufactured with all the raw materials that entails.

So, if you want to show people you care about the environment, enjoy looking smug at dinner parties or star in Hollywood blockbusters, then the Prius is the car for you. If you simply want to save fuel & money, lower your carbon footprint and actually do something for the environment, then improve your driving style and follow the example of Will from Warwick.

(1) www.mailonsunday.co.uk/news/article-399074/The-great-mileage-rip-off.html

(2) http://www.timesonline.co.uk/tol/driving/used_car_reviews/article3552994.ece

(3) http://blogs.warwick.ac.uk/nho/entry/911_mpg_in

Source: Clear analysis

Clear are launching a new carbon offset product for skydivers everywhere. The impetus for this has been Steve Baker, a customer who asked if we could figure out, then offer a product for skydivers who want to go carbon neutral.

So how is this figured out? Well, Steve kindly asked various drop-zones for their fuel usage per drop and jumper capacities for various aircraft. Using fuel burn figures, we calculated the CO2 per jump to be roughly 20-25kg.

Clear are now offering skydivers the opportunity to purchase jump packages of 100, 200, 500 & 1000 jumps.

And if you like, we’ll also provide you with a complimentary certificate as proof of your offset. Please visit contact us for more information.