Last month's outbreak of fuel contamination in Britain showed how dependent modern cars are on the computers hidden inside them.
Because of a small quantity of silicon in a batch of petrol from a refinery in southeast England, hundreds of motorists found their cars would only run very slowly, if at all. This wasn't because the petrol had damaged the engines - older cars drove on perfectly well - but because a chip onboard had decided that there was a danger and gone into nanny mode, shutting off most of the engine's power.
These electronics, and the chips that hold their programs, are everywhere in a modern car - the top-of-the-range Mercedes has 57 different sensor systems - but any car will have at the very least its engine, brakes and suspension controlled by embedded computers.
At present the chips are controlled either by the manufacturers or by really dedicated petrolheads. However, they could at some stage be controlled so that speeding would become not merely illegal but impossible.
Cars sold in Europe are fitted with software to stop them exceeding 248km/h. The heart of these electronics is the Engine Control System, or ECU. The basic function of an ECU is to control the fuel injection system and the timing of the spark plugs. And what the manufacturers won't program into their cars, the petrolhead performance companies are happy to attempt. Ian Crabb is a partner in Big Performance, and a former motorbike racer who cares a lot about speed. His current ambition is to drive a Smart car at 240km/h.
The electronics themselves, he says, are built into the components made by a few really big companies - Bosch, Siemens, or Delphi - who also employ the programmers who write their firmware. But since these components must be tunable, the performance maps, which specify exactly how the engine should behave at different speeds, can be downloaded from the EEPROM (Electronically Erasable Programmable Read-Only Memory) chips on which they are stored.
It is not just speed cameras that threaten the future. It is the idea that ECUs might in future respond to radio signals.
An ECU that could be reprogrammed by radio could make speeding impossible. A transmitter by a school could slow passing traffic down to 15mph. If this technology were coupled with individual transponder chips, stolen cars could be immobilised or crippled just as stolen mobile phones can be shut off.
The technology for this exists already. It could perfectly well be justified on environmental grounds, or as a means of stopping crime and terrorism. That it would also mean absolute chaos if the government's software crashed - or if hackers cracked its codes - might not occur to anyone until too late.