Toyota Motors and and the US National Highway Traffic Safety Administration (NHTSA) recently announced a recall of 55,000 floor mats for various Toyota and Lexus models following an investigation into a crash of a Lexus ES 350 on 28 August 2009 that killed a 45 year old police officer and three family members. The car sped out of control and finally hit another vehicle. Suspicions center on an All-Weather floor mat that could have got entangled with the accelerator pedal.

Floor mat problems in cars are not that uncommon. My previous car was an Audi A4 and there the mats provided by the dealer (it was a second hand car) did not fit the nipples meant to match up with holes in the mats. As a result, the driver side mat always kept sliding forward under heel pressure and sometimes ended up under the pedals (luckily never over the pedals!). One day my wife and I wondered why the car suddenly had a hard time accelerating (it felt really sluggish), until I realized what had happened and pulled the thick mat back out from under the accelerator pedal, which could not be depressed properly (presumably braking would have been similarly affected, but luckily I did not have to find out).

The opposite problem of unintended acceleration tends to be far more severe than a lack of acceleration, of course. An accelerator stuck on full throttle is something that happened to me once while driving a VW Santana, back in the 1980s.

That 5 cylinder engine still used a carburetor, not fuel injection. At some point the cold start enrichment mechanism of the carburetor developed a problem. I reported this issue to the dealer before a service and asked them to fix it. I don’t know what they did about it, but the next weekend I took the car on a German autobahn and had a very unpleasant incident where it got stuck at full throttle while I was doing over 160 kph (there was no speed limit there).

I found that the car kept accelerating even if I took my foot off the pedal and reached about 180 kph. I then pushed the brake pedal as hard as I could and at least it didn’t accelerate any further and slowed down a little. I depressed the clutch pedal (the closest manual equivalent of putting it into Neutral). Without any load on the engine, the RPMs shot up to the max but were limited by the engine management. With the engine roaring at maybe 5800rpm, the car coasted on the straight road and the brakes could slow it down. Worried about the engine I then switched off the ignition, which did stop the engine but also disabled the brake servo and power steering. I quickly turned the ignition back on, but not far enough to engage the starter, just so the steering lock could not be activated by turning the steering wheel as it would with the ignition completely off. I finally brought the car to a complete stop on the hard shoulder, without brake servo assistance.

After opening the bonnet, I opened the carburetor with a screw driver from the emergency set in the back and found the butterfly valve stuck. After some prodding with my fingers, it went back to the proper position and I could resume my journey, with no further incident.

I can see that using the brake pedal, my first reaction in that situation, would not have been as effective in a 3.5 litre V6 Lexus as it was in my 2 litre VW, because the engine was far more powerful. Switching the car to Neutral, my second reaction, would have been quite effective in the Lexus though. My third reaction, switching off the engine, would have been quite impossible for the average driver in that loan car. Turning off an ignition key is one thing, but having to hold down the power button for three seconds (as in that Lexus and some other cars that use a start button instead of an ignition key) rather than just pushing it once is anything but intuitive. Yes, mobile phones and computers can be shut down that way too, but most of us grew up with cars that behaved differently from today’s computers. Actually, even when I started with computers they switched off as soon as you pushed the power button once. I can see how the driver would push the power button once to turn it off and nothing would happen. Then what?

If the driver missed his chance to shift the gear into N, he would likely run out of time in that car before hitting another vehicle in front, before he would have figured out how this is supposed to be done.

Most accidents occur due to a combination of errors. In this case it appears to have been the floor mat problem, combined with the driver missing the chance to respond effectively by shifting the gearbox to N.

Problems with stuck accelerators could have been ameliorated in the engine management by having the brake pedal override accelerator input. If for example the brake pressure was high enough for an emergency stop (the ABS has a sensor for that) then the fuel injection quantity could be limited to idling or at least significantly less than full acceleration would demand, effectively ignoring the accelerator, floor mat or no floor mat. The only side effect I can see is that it would make drag racer starts impossible.

When I explained about the recent Toyota problem to my wife, she replied that she had tried to remove the mats from our 2008 Prius for cleaning but didn’t manage to because the hooks held them in place too firmly. Even without the hooks I imagine the left foot rest in the Prius would stop the mat from moving much.

Whatever car you drive, make sure the floor mat is secured against sliding around. If you’re not sure, better get rid of it altogether. And if you should ever find yourself with a car accelerating out of control for whatever reason, remember that the N position of an auto box or clutch pedal of a manual will always disconnect the engine from the gearbox, not matter what causes the engine power to surge.

On August 11, 2009 GM made media headlines by claiming that using EPA methodology its Chevy Volt hybrid vehicle was capable of getting a city driving fuel economy rating of 230 miles to the gallon. That’s 98 km/l or 1.02 l/100 km to those of us on the rest of the planet who use the metric system. The next day the EPA poured cold water on GM’s claims: “The EPA has not tested a Chevy Volt and therefore can’t confirm the fuel economy values claimed by GM.” Relatively few articles took the trouble of dissecting GM’s claims for plausibility.

In reality any mpg figure for this type of vehicle is essentially meaningless because unlike mpg figures for other cars it is highly dependent on how far one drives the Volt between recharges. Volt uses a lithium ion battery with a theoretical capacity of 16 kWh that powers the car for about 40 miles (64 km), depending on driving conditions. Once the battery reaches its lower charge limit, a 4 cylinder gasoline engine kicks in to power a generator to provide electricity for driving. GM calls this internal combustion engine (ICE) the “range extender”.

Do less than 40 miles between charges and the Volt won’t burn any gasoline. Its mpg rating would be infinite, because its only fuel is measured in kWh and shows up on your electric utility bill. Once you exceed the 40 mile limit you will start burning gasoline at a yet unknown rate. The Wikipedia article on the Volt mentions a figure of 50 mpg, almost the same as the third generation Toyota Prius. I am a bit skeptical about that number, given the Prius uses an efficient mechanical transmission that connects the engine directly to the wheels via planetary gears, while the Volt first converts the mechanical power from the engine into electricity and then an electric motor converts the electric power back into mechanical power. Neither process is 100% efficient. Also, at 170 kg the Volt’s lithium ion battery weighs some 125 kg (280 lbs) more than the Prius’ much smaller 45 kg nickel metal hydride (NIMH) battery. This weight difference is not exactly going to help the Volt match the Prius’ fuel economy in city driving, where weight is a major determining factor.

For argument’s sake, let’s assume that the Volt does indeed get 50 mpg while running on the engine, after 40 miles on battery power. So what’s the total test distance in GM’s calculation that it used as the basis for its claim? The portion run on gasoline would be 50/230 of it and the 40 electric miles would be the remaining 180/230. From that we can calculate that the total distance is about 51 miles (40*230/180), of which 11 are on gasoline. You would get 230 mpg only if you happen to go 51 miles between recharges. On the other hand, it could be 83 mpg at 100 miles between charges or even 2550 mpg at 41 miles. Pick your number 😉 It really won’t tell you anything until you also factor in your driving patterns and the cost of domestic electricity for recharging where you live.

Americans basically like big numbers and a figure of 230 mpg sure is eye catching, but it doesn’t really tell you much until you study all the details. Here’s another big number: $40,000. That’s about how much GM is going to charge for the Volt from late 2010 or early 2011, when it’s supposed to go on sale. $15,000 more than a 51 mpg (EPA city rating) Prius III is tough to justify economically: Even at $5 per gallon it would buy 3000 gallons or probably around 120,000 miles at a conservative 40 mpg and no electric bill. It remains to be seen how the brand new lithium ion batteries in the Volt will hold up over time compared to the tried and tested NiMH batteries used in the Prius for the last 12 years. The Prius batteries are backed by an 8 year warranty and there are cars that have done 400,000 km (250,000 miles) on the first traction battery.

The 230 mpg claim is dishonest. They could simply say: “It doesn’t use any gasoline for about 40 miles and after that it gets 50 mpg (or whatever number).” That wouldn’t be too hard to understand for anyone and wouldn’t raise any unrealistic expectations. GM doesn’t even mention what fuel economy the car gets while running on the range extender.

I have to agree with those who charge that GM designed the Volt less as a viable competitor in the low-carbon automobile market than as a clever insurance policy to make a bailout at US tax payers’ expense more palatable to the public. Its technology sounds exciting, but it’s a farce. The main piece of new technology that goes into the car – its lithium ion batteries – will be made by LG in Korea. The rest of the car is basically the same platform as the Chevrolet Cruze and its European sibling, the Saab 9-3.

Let’s remember that Toyota launched the first generation Prius in Japan back in 1997. GM didn’t see the writing on the wall then: Even two years later it went out and bought the Hummer brand. Over the following decade it saw its own market capitalization drop from over $50 billion to essentially zero and would be dead by now but for the assistance of politicians too scared to see GM and its supply chain fail while the country was still heading into the worst recession in decades. Keeping the Volt alive all this time made political sense for GM, whatever the real merits of the project.