Designing Shared Cars

Almost 10 years ago I blogged about car sharing companies in Melbourne [1]. Since that time the use of such services appears to have slowly grown (judging by the slow growth in the reserved parking spots for such cars). This isn’t the sudden growth that public transport advocates and the operators of those companies hoped for, but it is still positive. I have just watched the documentary The Human Scale [2] (which I highly recommend) about the way that cities are designed for cars rather than for people.

I think that it is necessary to make cities more suited to the needs of people and that car share and car hire companies are an important part of converting from a car based city to a human based city. As this sort of change happens the share cars will be an increasing portion of the new car sales and car companies will have to design cars to better suit shared use.

Personalising Cars

Luxury car brands like Mercedes support storing the preferred seat position for each driver, once the basic step of maintaining separate driver profiles is done it’s an easy second step to have them accessed over the Internet and also store settings like preferred radio stations, Bluetooth connection profiles, etc. For a car share company it wouldn’t be particularly difficult to extrapolate settings based on previous use, EG knowing that I’m tall and using the default settings for a tall person every time I get in a shared car that I haven’t driven before. Having Bluetooth connections follow the user would mean having one slave address per customer instead of the current practice of one per car, the addressing is 48bit so this shouldn’t be a problem.

Most people accumulate many items in their car, some they don’t need, but many are needed. Some of the things in my car are change for parking meters, sunscreen, tools, and tissues. Car share companies have deals with councils for reserved parking spaces so it wouldn’t be difficult for them to have a deal for paying for parking and billing the driver thus removing the need for change (and the risk of a car window being smashed by some desperate person who wants to steal a few dollars). Sunscreen is a common enough item in Australia that a car share company might just provide it as a perk of using a shared car.

Most people have items like tools, a water bottle, and spare clothes that can’t be shared which tend to end up distributed in various storage locations. The solution to this might be to have a fixed size storage area, maybe based on some common storage item like a milk crate. Then everyone who is a frequent user of shared cars could buy a container designed to fit that space which is divided in a similar manner to a Bento box to contain whatever they need to carry.

There is a lot of research into having computers observing the operation of a car and warning the driver or even automatically applying the brakes to avoid a crash. For shared cars this is more important as drivers won’t necessarily have a feel for the car and can’t be expected to drive as well.

Car Sizes

Generally cars are designed to have 2 people (sports car, Smart car, van/ute/light-truck), 4/5 people (most cars), or 6-8 people (people movers). These configurations are based on what most people are able to use all the time. Most car travel involves only one adult. Most journeys appear to have no passengers or only children being driven around by a single adult.

Cars are designed for what people can drive all the time rather than what would best suit their needs most of the time. Almost no-one is going to buy a personal car that can only take one person even though most people who drive will be on their own for most journeys. Most people will occasionally need to take passengers and that occasional need will outweigh the additional costs in buying and fueling a car with the extra passenger space.

I expect that when car share companies get a larger market they will have several vehicles in the same location to allow users to choose which to drive. If such a choice is available then I think that many people would sometimes choose a vehicle with no space for passengers but extra space for cargo and/or being smaller and easier to park.

For the common case of one adult driving small children the front passenger seat can’t be used due to the risk of airbags killing small kids. A car with storage space instead of a front passenger seat would be more useful in that situation.

Some of these possible design choices can also be after-market modifications. I know someone who removed the rear row of seats from a people-mover to store the equipment for his work. That gave a vehicle with plenty of space for his equipment while also having a row of seats for his kids. If he was using shared vehicles he might have chosen to use either a vehicle well suited to cargo (a small van or ute) or a regular car for transporting his kids. It could be that there’s an untapped demand for ~4 people in a car along with cargo so a car share company could remove the back row of seats from people movers to cater to that.

Voltage Inside a Car

I previously wrote a post with some calculations about the power supplied to laptops from a car battery [1]. A comment on the post suggested that I might have made a mistake in testing the Voltage because leaving the door open (and thus the internal lights on) will cause a Voltage drop.

So I’ve done some more tests:

Test Voltage
battery terminals 12.69
front power socket with doors closed 12.64
front power socket with doors open OR ignition switch on 12.37
cigarette lighter socket with ignition switch on 12.32
front power socket with doors closed and headlights on 11.96
front power socket with engine running 14.38
front power socket with engine running and headlights on 14.29

In my previous tests I recorded 12.85V inside my car (from the front power socket which although having the same connector as a cigarette lighter isn’t designed for lighting cigarettes) and 13.02V from the battery terminals – a 0.17V difference. In my tests today I was unable to reproduce that but I think that my biggest mistake was to take the reading too quickly. Today I noticed that it took up to a minute for the Voltage to stabilise after opening a door (the Voltage dips after any current draw and takes time to recover) so a quick reading isn’t going to be accurate.

My car is a Kia Carnival which has two sockets in the front for power and for actually lighting cigarettes. The one for lighting cigarettes has a slightly lower Voltage and only works when the ignition is turned on. The car also has a power socket in the boot (the trunk for US readers) which delivers the same Voltage as the power socket in the front.

Also one thing to note is that today is a reasonably cold day (16.5C outside right now) and my car hasn’t been driven since last night so the battery would be quite cold (maybe 12C or less). My previous measurements were taken in summer so the battery would have been a lot warmer and therefore working more effectively.


The Voltage drop from turning on the internal lights surprised me, I had expected that a car battery which is designed to supply high current wouldn’t be affected by such things. Certainly not to give a 2% Voltage drop! The Voltage difference from reading inside the car and at the battery terminals might be partly due to the apparent lead coating on the terminals, I pushed the probes of my multimeter beneath the surface of the metal and got a really good connection.

The 14% Voltage increase when the engine was running was also a surprise. It seems to me that if you are running a power hungry device (such as a laptop) it would be a good idea to disconnect it when the engine is turned off. A 14% higher voltage will give a 14% lower current if the PSU is efficient and therefore less problems with heat in the wiring and less risk of blowing a fuse.

Also it’s a good idea to be more methodical about performing tests than I was before my last post. There are lots of other tests I could run (such as testing after the engine has been running for a while) but at the moment I don’t have enough interest in this topic to do more tests. Please leave a comment if there’s something interesting that you think I missed.

Seatbelts and Transporting Computers

I’ve just read an interesting post at Making Light about seat-belts [1].

In Australia seat-belt use is mandatory, you can be fined for failing to wear one – and the police (who help clean up the mess when someone dies on the road) are apparently quite aggressive about enforcement. Even aside from the legal requirement the use of seat-belts is fairly ingrained in Australian culture, people tend to use them even when they won’t get caught.

One of the things I like to do in my spare time is to take unused computer gear from IT companies (which they regard as rubbish) and give it to home users for recreational and educational use. Due to that and my work for some smaller IT companies I’ve helped many people load computer gear into their private cars and observed that most people will not take adequate care unless I coerce them.

A CRT monitor tends to be large and heavy, you wouldn’t want to get hit in the back of the head with one at 60Km/h. With some combinations of monitor and car you can fit a monitor in the front passenger foot-well, but usually the only place a monitor will fit is the back seat. The correct thing to do is to use the seat-belt to strap the monitor in place. It’s most likely that the monitor stand (the only part that allows a seat-belt to be attached) would snap off in the event of a serious crash – but this would at least slow the monitor down. Also don’t put the monitor directly behind your seat if you can avoid it, put it behind the passenger seat. In a collision monitor might be able to push through your seat and cause you a back injury.

Between 1992 and 2006 there were 78,000 acute computer-related injuries treated in US hospital emergency rooms [2]. The number of injuries caused by monitors peaked at 37% of the total in 2003 – this was largely due to monitors falling on people. Even without the speed of a car a monitor can be a dangerous projectile.

Hard drives have a lot of potential to cause damage, they are dense, hard, and the corners often aren’t rounded. Storing them above the back seat behind the driver’s head (as a friend once tried to do) is a really bad idea. Mythbusters showed that a box of tissues isn’t going to kill you in a crash, but a hard drive is much more dangerous. The typical car glove box can store a few drives. If you need to transport a box full then the front passenger foot well is a reasonable place. If your car rolls then that would suck, but it seems that people usually die when they roll their car anyway so just try not to do that.

A serious server (EG 2RU or bigger rack-mount) typically weighs 30Kg or more and is solidly constructed. The size and mass of such a machine makes it extremely difficult to safely store inside a car. The ideal place is the boot, but if that isn’t an option then behind the passenger seat is the next best option.

One final issue that I’ve been wondering about is the safest option for laptops that are in use in a moving car. A 3Kg Thinkpad would have to hurt if it hit you in the back of the head at 60Km/h. The child-seat attachments are solid anchor points that can be used for other things. I wonder if a laptop security cable could be attached to one of the child seat points. According to an exhibit at a science museum I can throw a tennis ball at 115Km/h, so I presume that laptop security cables are designed not to break when someone swings the laptop at that speed. Therefore if a car was driving at a legal speed in Australia before crashing then a laptop security cable should be able to stop the laptop. Preventing the cable from injuring the passenger on the way would be the difficult part.

Designing Unsafe Cars

The LA Times has an interesting article about problems with Toyota and Lexus cars [1]. Basically there are problems where the cars have uncontrolled acceleration (there seems to be some dispute about whether it is due to engine management or the floor mat catching the accelerator pedal). When that happens the brakes don’t work (due to the vacuum power-assistance for brakes going away when the engine is at full power) and a terrible crash seems inevitable.

There are suggestions that the driver should shift the car to neutral and discussion about how the Toyota gear selection makes that difficult. Some years ago I was driving an automatic car on a freeway at 100Km/h and the engine stalled (due to a problem with the LPG system). I had become used to never touching the gear lever while driving so the possibility of moving the gear lever one notch to neutral didn’t occur to me. With a dead engine in gear the car slowed rapidly which is quite dangerous when surrounded by 100Km/h traffic. Fortunately I was able to swerve into the emergency lane (across one lane of active traffic) before the car slowed much. That was in a relatively controlled environment with a gear shift mechanism that is a lot simpler than that which is common in some of the more expensive cars.

According to Wikipedia the maximum speed limit in the US is 80M/h [2]. It seems to me that Toyota is being irresponsible by selling cars that can sustain 120M/h, while the probability of surviving a crash at 80M/h is quite low, it seems likely to be a lot greater than the probability of surviving a crash at 120M/h. Also if a car is out of control at 80M/h then the driver will have a lot more time to work out how to put the engine in neutral or turn it off – the lower speed will extend the time available by more than 50% because bends in the road can be better handled at 80M/h.

It seems to me that it would be a feature for the car owner to have the car limited to a speed that is not much greater than the speed limit. According to Wikipedia the highest speed limit in Australia is 130Km/h (in NT), but it’s 110Km/h in all places where I have driven. If my car had a governor to limit the speed to 115Km/h and a switch to change the limit to 135Km/h in case I ever drive to the NT then it would not affect my driving patterns (I rarely drive on roads with a 100Km/h limit and almost never drive on roads with a 110Km/h limit) – but it could reduce the probability of things going horribly wrong. Also one thing to note is that last time I checked car tyres sold in Australia were only required to operate safely at speeds below 190Km/h (118M/h), so a Lexus that went out of control at 120M/h in Australia might risk a tyre blow-out – which admittedly would only make things marginally worse.

A governor for the reverse gear would also be a good feature. Some time ago a granny got her foot stuck on the accelerator in a car park and caused serious damage to her car and a parked car – after passing close by where I was standing. I don’t think that there is a real need to do more than 5Km/h in reverse, limiting the speed would give pedestrians a better chance of escaping parking accidents.

One serious problem with some of the Toyota and Lexus vehicles is that it apparently takes 3 seconds to turn the engine off in an emergency! I’ve been driving for almost 20 years and experienced a number of dangerous situations, all of which were essentially resolved (for better or worse) in significantly less than 3 seconds. A 3 second delay is as good as a 1 hour delay for safety critical systems.

Also if the accelerator and brake pedals are pressed at the same time then the brake should take precedence. It seems quite obvious that whenever both pedals are pressed hard then the driver would probably prefer hard braking to hard acceleration.

If you look at industrial machinery (robots, lathes, etc) you will always see big red buttons (or whatever color is used for emergency stop in your region) that are clearly marked and obvious – to the workers and to bystanders. Escalators have less obvious red buttons but they can still be shut down in an emergency. It seems to me that there are potential benefits to having an emergency shutdown button in a car, maybe in a position that is accessible to the front-seat passenger in case the driver is incapacitated. Such a shutdown button wouldn’t do anything extreme such as fully activating the brakes (which would be very bad on a road that has high-speed traffic), but would prevent acceleration (with some sort of hardware control to avoid software problems) and maintain power to the brakes and the steering.

One thing that needs to be considered is that people tend not to do the most logical things when in an emergency situation. It needs to be possible to do whatever is necessary to save your life without any great deal of thought. Pushing a big red button is easy, holding down the “on” button for 3 seconds or even navigating a gear shift to an uncommon setting is a lot more difficult.

It seems to me that there is also an issue of driver training. If putting an automatic car into neutral and cruising to a stop was part of the test for new drivers then the results of such car problems might not always be so bad.

But I don’t expect there to be any serious changes to driver training or car design. People are too accepting of road deaths.

Don Marti has expressed a plan to never buy a vehicle with an automatic transmission because of this issue [3]. But the number of new vehicles being sold with a manual transmission is steadily reducing. An automatic transmission allows better performance (F1 cars have used them for ages), better fuel efficiency (you could never make a manual Prius), a more comfortable ride (the Hybrid Lexus keeps winning the Australian Luxury Car of the Year award), and allows less skillful drivers. Unless Don wants to ride a moped or drive an old car then I expect that he will be forced to get an automatic transmission. Then of course he will still be at risk of other people having car problems (the LA Times article mentions a third party being killed after an out of control car hit them).

Also I expect that the extra safety features that are implemented in luxury vehicles such as the Lexus would save a few lives, they should save enough to outweigh the number that are lost on the rare occasions when the car goes out of control. Other luxury cars such as the Mercedes S class have great safety features and don’t have a history of going wrong in a newsworthy way. A second-hand S Class Mercedes was surprisingly cheap in the UK last time I checked, cheap enough to make it worth considering the importation of one to Australia.

But my solution to these problems is to try and minimise my driving. A 1.5 ton Lexus driving out of control at the maximum speed possible in urban streets won’t do much damage to a 20 ton tram.

The Future of Electric Cars

TED published an interesting interview with Shai Agassi about electric cars [1]. One idea that I hadn’t heard before is that of moving car batteries between regions as they lose capacity. An old battery for an electric car that can only handle short journeys may be useful in a region where journeys are typically short. On a similar note I expect that in a few decades the less prosperous countries will import old electric vehicles and fit them with 4 or more batteries. Last time I checked the Prius battery pack weighed about 120Kg, so the car would be usable with 4 battery packs if driven at low speeds.

Shai Agassi also gave a TED talk on this topic [2]. The real solution for the problem of providing convenient and affordable electric vehicles is to start by recharging the batteries whenever the vehicle is parked (at the office, shopping center, home, etc). Then on the rare occasions when the car is being driven for longer distances and the battery gets flat it can be swapped for a charged battery. They have apparently designed a robot for changing car batteries, so changing the battery would be like driving through a car-wash. He describes this as an economic model that decouples the expensive battery from the car, so you pay for the use of the battery not the ownership – just as with a petrol car you pay for the petrol you use not for a portion of the ownership of an oil well.

He also pointed out that cars produce 25% of the world’s CO2 emissions, so his plan for all electric cars everywhere seems to be an essential part of solving the environmental problems. He then compared this to the UK parliamentary discussion on ending slavery, at the time slaves provided 25% of the energy used by the UK. After a month of discussion the decision was made to make the moral choice and end slavery regardless of the cost.

Real-World Car Safety Tests

The car safety tests that are required for every new mass-market passenger vehicle are flawed in many ways. Here is a list of the most obvious flaws (please point out any that I’ve missed):

  1. There has been no research to make accurate crash-test dummies to represent women and children, and I believe that there has been no research to make crash-test dummies to accurately represent people of racial groups that are not common in the US. Basically the medical research used to make crash test dummies was performed on male cadavers that were readily available in the US.
  2. The standard tests involve a direct collision with a centrally targeted stationary object, a direct collision with an offset stationary object, and solid objects (representing cars) hitting the vehicle from the read and the side. These simulate crashes where there is little or no attempt made to avoid the collision, they are probably really good for protecting drunk drivers. But any sane and sober driver is probably going to make some effort to avoid the collision and the resulting impact will not be at a multiple of 90 degrees. Note that when a car directly hits the side of a moving car it is quite different to hitting the side of a stationary car (which is what is tested).
  3. There are no standard tests for the probability of a vehicle rolling in the event of a crash or of what would happen to the occupants if it was to roll. Rollover crashes are among the most dangerous…
  4. The tests do not take into account the ability of the driver to avoid a crash or minimise the damage. The ability to avoid crashes is a major advantage for cars with a low center of gravity, AWD, and traction control. It’s a major problem for vehicles with a high center of gravity and with tires that are not designed for road use (IE 4WD/SUV vehicles).

But generally the crash-test results are of some use provided that you start by looking at the results from vehicles that have good safety features such as the Audi Quattro, the AWD version of the VW Passat, a Mercedes with 4MOTION, or any other vehicle with constant four wheel drive, road tires, four wheel traction control, and a low center of gravity.

The RACV (the main car owners advocacy organisation in Victoria and also a major car insurance company) [1] has published the used car safety ratings report [2]. This was produced by the Monash University Accident Research Centre and is based on the analysis of 3,000,000 crashes reported to police in Australia and New Zealand. Results are only available for cars which have been in common use on Australian and New Zealand roads for some time (so there aren’t many entries for vehicles that are less than 5 years old or for particularly expensive vehicles).

The report also includes estimates on the purchase prices of some of the safest vehicles. A vehicle that is significantly better than average can be purchased for as little as $5000!

Now if you want to buy a new vehicle then choosing the latest version of a model that has rated well on the used-car tests should be safe if the new car crash tests also report good results. It seems likely that the latest Mazda 6 or VW Passat will also rate well on the used-car tests in a few years time. It’s a pity that the report didn’t note which of the vehicles that rated well have models that have good features to avoid collisions such as EBA, ABS, AWD, and traction-control.

A friend who is active in the free software community recently had a very lucky escape from a significant crash. From his description I doubt that car safety features had much to do with him escaping without injury, I think that it was mostly luck. While his car did have a good range of safety features (and was rated well on the used-car tests), a high-speed collision that involves a truck can easily result in a car being squashed flat. I have already sent him the RACV link which he is using as part of the process to decide what new car to purchase. But I think that this information needs to be spread more widely.

I have not searched for information on such analysis of crashes being performed in other countries, please leave a comment if you know of any good research that will be useful for other people. One thing to note however is that given the global scope of car manufacturing, results from one country will have some validity in others. I expect that a VW Passat that is sold in Germany or the US will be almost identical to the Australian version.

Inhaling Petrol Fumes

Tonight at 6PM the channel 7 news will have a special report about the dangers of inhaling fumes while filling cars with petrol. I’m blogging now because based on past experience I expect almost no technical content in the report and that the advert for the news show contains everything that is useful.

The advert showed that they had used some film technique to show the fumes leaving the petrol tank while fuel is pumped in. It was obvious that the fumes were rising past the face of the man who was filling the tank. Not that this is really news, if you observe closely when fuel is pumped into a car you can see where the vapor escapes as the slight difference in density causes whatever is behind it to shimmer slightly.

For a long time the Prius has had a bladder inside the fuel tank which expands and contracts to match the fuel volume [1]. This greatly reduces the evaporative loss of fuel when the car is parked and the ambient temperature changes and also when fuel is pumped in. So it seems that in regard to the issue of fuel vapor poisoning the driver, the Prius has been better than other cars for about 10 years. Apparently Toyota have developed a new system that they have implemented in the Hybrid Lexus and the new Hybrid Camry which involves “vapor recovery”, this is supposed to give similar benefits in terms of not releasing petrol fumes into the environment but without limiting the capacity of the fuel tank in cold weather (a common complaint about the Prius). I have not been able to find any technical information on how this works (please let me know if you know a good web page about it).

The next issue is that any car which gives good fuel efficiency and has a reasonable size petrol tank will be better in regard to vapor releases. The less frequently you need to refuel your car the less fuel vapor you will inhale. I predict that channel 7 will not suggest that people drive fuel efficient cars, they are probably more likely to go for hand-wringing about the “inevitable” health problems, or make vague claims that the government should do something about it. The fact that the news show in question is immediately followed by “Today Tonight” (one of the tabloid TV shows) is an indication of the likely quality.

A final issue is the puddles of fuel that you commonly see at petrol stations. People regularly spill reasonable quantities of petrol and Diesel fuel and it just accumulates on the concrete. It’s not uncommon that I will have to drive with my car windows open after buying petrol due to the petrol that I stood in evaporating from my shoes. Apart from training people to not be stupid when refueling their vehicles I can’t think of any way of solving this problem. A petrol station employee once told me that it’s not uncommon for people to refuel cars with their young children standing within splash range of the fuel nozzle. If people can’t manage to avoid splashing their children with fuel then it seems that it will be impossible to get them to do anything reasonable or intelligent regarding the refueling process.

The Cost of Car Crashes

An article from 1999 suggested that car crashes caused a financial loss in OECD countries equivalent of 2% of their entire economies [1]. An article from the Sydney Morning Herald in 2001 gave a conservative estimate of the cost of a road fatality at $1.5 million [2], it also notes that due to different analysis methods American transport economists derived a figure of $5.5 million. $1.5 million in 2001 adjusted for CPI would be close to $2 million now.

Currently that $2M cost is an externality of the car industry. Most of it is paid by the government, IE we all pay for it through our taxes. This means that there is little financial incentive for drivers and car companies to make the roads safer. Many of the attempts to legislate road safety fail due to the legal system being unable to manage the rapidly changing range of vehicles on the market.

The insurance companies have very detailed analysis of the relative safety of vehicles, so it seems that the only sensible way of enforcing safe driving is through economic measures implemented via insurance.

I believe that for every person who is killed or seriously injured on the road a fine of $2M should be levied. Every driver should be compelled to have insurance to cover such fines (driving without insurance should be illegal).

Then the government could cease being involved in regulating what types of car someone can drive. If someone who is less than 25 years old can get insurance for a turbo-charged car then it probably means that a statistical analysis suggests that the combination of driver and vehicle is likely to be reasonably safe (EG there are many turbo-charged cars on the market that are not particularly fast).

Now this will increase the car insurance costs for everyone, but it will decrease the amount of general tax money that is spent on issues related to road fatalities, which would allow the income tax rates to be decreased. This means that any tax-payer who has a good driving record and who drives a type of car that tends not to be crashed could expect to save money overall. Any tax-payer who doesn’t drive a car would save even more money.

But the main point of this idea is to increase road safety by forcing bad cars and drivers off the road. Currently defective cars are only removed from the road if police notice something unsafe about them and cite them for being unroadworthy – this only happens if it’s a problem which can be observed from outside the vehicle (EG worn tires or broken lights). In some states elderly drivers have no requirement for periodic health checks to determine their ability to drive, I know of one case of a woman who was certified as legally blind, ordered a white cane, and then drove home afterwards! I’m sure that insurance companies would implement whatever tests are necessary to reduce the risk of being hit by multiple $2M fines from a single crash.

Hyperthermia and Children in Cars

Bruce Schneier writes about the risks involving children abandoned in cars and cites an article about the tragic deaths of children in hot cars [1]. One unfortunate error that he made was to not cite the following from the end of the last page of the Washington post article he cited [2]:
In hyperthermia cases, he believes, the parents are demonized for much the same reasons. “We are vulnerable, but we don’t want to be reminded of that. We want to believe that the world is understandable and controllable and unthreatening, that if we follow the rules, we’ll be okay. So, when this kind of thing happens to other people, we need to put them in a different category from us. We don’t want to resemble them, and the fact that we might is too terrifying to deal with. So, they have to be monsters.”

I believe that similar thought processes are used in relation to many other situations, and that such thought processes prevent people from taking appropriate actions to minimise the risk. If someone considers that forgetting a child in the back seat to be an accident that could happen to anyone then they would be inclined to take action to minimise the risk (such as spending some money on a sensor). If however they consider such forgetfulness to be proof of being a “bad parent”, then as they are a “good parent” they would have to avoid buying a monitor. I’m surprised that Bruce didn’t draw an analogy between this and the forgetful losses of laptops and guns by people who work for law enforcement agencies (which he has written about before).

I wonder how expensive it would be to make a sensor for heart-rate, breathing, and temperature integrated with a GSM modem and a GPS? If it could be small enough to be attached to clothes then the child could wear it at all times.

If such a sensor was to detect a sign of a problem it wouldn’t matter whether the child was forgotten in a car, at day-care, or even being actively supervised. The data would be sent to the monitoring agency along with GPS data. The monitoring agency could then phone the parents. If the parents don’t answer or don’t know where the child is then the police could track down the GPS location. Probably most calls would be due to parents leaving a child too close to an air-conditioner or playing outside in the sun in summer which are unlikely to give a fatal result and a phone call would get a quick fix for what would only be a minor health problem.

If the device was marketed as monitoring for “sleep apnia” then parents could buy it without admitting to the possibility that they might do anything wrong. The causes of SIDS are a topic of ongoing research and parents can admit to being worried about their children suffering from it without admitting any possibility that they might make a mistake.

Used Car Prices

There is an interesting article in The Age about the effect of petrol prices on the poorer people in Melbourne [1].

The article claims that people are unable to sell large old cars and buy smaller cars. To investigate that claim I did a price search on Ford Falcons and Holden Commodores on the web site . The Ford Falcon and Holden Commodore were for a long time the two leading marques of cars sold in Australia – both of them large cars. It seems that if I wanted to buy a Falcon that is less than 20 years old with an engine of 4.0L (or bigger) then I would have many choices available with list prices under $2500, including some cars in that price range which are as little as 10 years old (the average age of a car that’s registered for use in Australia). For Commodores there seems to be less choice, there are a few of them with 4L engines that are just over 10 years old being advertised for just under $5000 and a significant number being advertised in the $5,000 to $7,500 range. I don’t know whether the increased asking price for Commodores is due to greater optimism by the owners or a greater demand. One thing that we have to keep in mind is that due to the low price of advertising on the web site and the duration of the advert (which permits changing the price at any time) the sensible strategy is to start the advert with an optimistic price, and then gradually drop the price if there is little interest by the buyers.

There are also some Falcons on auction on Ebay that are going fairly cheaply, one example is less than $6000 for a 2000 Falcon with only a few minutes to go.

The HSV (Holden Special Vehicles) cars are listed on Drive as a different make on Drive (it’s just Holden’s range of faster vehicles), and surprisingly their prices are quite strong. There is only one vehicle on offer for less than $5000, and only a few for less than $10,000.

Now when it comes to buying a small car, on ebay there are a number of Toyota Corollas on sale, two 1997 models are on sale for just under $9,000 and just under $10,000. It seems that you could sell a 2000 model Ford Falcon on ebay and not receive enough money to buy a 1997 Toyota Corolla!

For the Corollas advertised on Drive the majority of them seem to be advertised for around $15,000, but the volume on sale is great enough that there is a significant minority advertised for lower prices. There are 173 Corollas advertised for between $2,500 and $5,000 it might be possible to find one of those that has no significant problems. So it seems that ebay is not the place to buy a Corolla!

So it seems that the main premise of the article (that you can’t sell a second-hand large car and buy a small car) is correct. If you were to sell a 1990’s Falcon or Commodore and buy a Corolla (which cost about half as much as a high-end Falcon or Commodore when new) of the same age then you would be lucky to get more than half the Corolla purchase price. Then of course there’s a 4% “stamp duty” tax to pay and the risk that a second-hand car you buy might have some hidden problem (the cheaper cars are unlikely to have been well serviced).