How buses are confusing high-tech cars

Speed signs on the back of Sydney buses are thwarting one of Europe's best safety items.

Numerous cars can read speed signs and the best can accelerate or brake to match the legal limits. But the hi-tech cameras used by Audi, BMW and Mercedes-Benz are confused by nonconforming speed signs, a major problem in Australia where sizes and shapes vary between states. Installing them at different heights also makes recognition tough.

BMW was the first to run into trouble some years ago with a 7 Series flagship that could not use its landmark European tech. However, it's the buses causing the biggest problem for Audi.

"The controls in Europe around the displaying of speed limits are generally tighter than we have in Australia, which makes it more straightforward for the car to interpret the information it sees via the camera," says Audi Australia spokesman Shaun Cleary.

We need to ensure it is reliable and accurate before we introduce it here.

I've just driven in Germany in an Audi A4 allroad quattro. The car's camera guidance — for adaptive cruise control, stop-and-go and speed sign recognition — means it can handle lots of freeway drudgery.

Set the cruise control and it adjusts smoothly to the limit, even through roadworks with temporary limits and signage.

"The functionality is currently available across most of our model range in Europe," says Cleary.

It's not nearly as easy here, particularly with buses that create a rolling speed zone.

"In Australia," Cleary says, "you might have a speed sign on the back of a bus, for example, that shows a lower speed limit than the signposted zone.

"This is confusing for the car because there's no significant visual differentiation from fixed signposts, like size or format, for the car to identify."

Prestige brands are chasing updates from Europe that can cope with varying Australian signage to ensure the tech eventually will work here.

"We need to ensure it is reliable and accurate before we introduce it here," says Cleary.

Would you trust an auto-adjusting cruise control system? Tell us what you think in the comments below.