What is a head up display (HUD)?

A head-up display or HUD, is a system which projects key information, such as vehicle speed, into the driver’s line of sight so they do not need to take their attention off the road while driving.

Not that long ago, this type of tech was reserved for only the most expensive cars, but it has begun trickling down into the mainstream.

Early systems were simple single colour affairs, but the latest generation of HUDs have full colour at their disposal. New and advanced systems incorporate features such as sat-nav and sign recognition into the information they display too.

There are currently 800 cars available on BuyaCar with a head-up display. Prices start at £8,990 and finance costs from £138 per month

What information does a head-up display show?

Your speed is usually the largest piece of information on your head-up display, shown as a precise number.

In cars fitted with cameras that can read speed limit signs, you'll often see the limit for the road that you’re on displayed.

If your car has sat-nav, then it's normal for directions to be displayed on the head-up display too. Typically, they won't appear when you're just following a road, but will be displayed when you're approaching a junction or exit that you've got to take.

The images are usually extremely simple: a single arrow, or an outline of a roundabout, so that it can be understood in an instant.

Some systems, such as those used by BMW, also include entertainment functions into the head-up display. It will display radio stations or your song list as you scroll through them using a button on your steering wheel.

What types of head-up display are there?

There are two main types of system. The cheapest and most common has a small screen that rises from the dashboard ahead of the driver onto which the information is projected. You might see this referred to as a combiner type HUD.

This pop-up solution is not particularly attractive or sophisticated, but it is effective, and easily adjustable to suit the driver. It's an option on cars such as the Mini Hatchback, Mazda 3 and Ford Focus.

The second type beams the information straight onto the windscreen from a small module on top of the dashboard, behind the speedometer. BMW uses this kind of system in many of its cars.

As well as looking less clunky, this type of integrated system gives the impression that the information is being displayed a few metres ahead of the vehicle. This helps the driver refocus their eyes from farther down the road to the HUD, and back again as quickly as possible. The driver can adjust the position of the projection should they desire.

In a similar fashion to aftermarket sat-nav systems, there are a handful of aftermarket HUD systems. Products by Navdy and Hudway claim to bring HUD technology to any car. Both are of the pop-up type, and  while the former is a standalone system that costs several hundred pounds, the latter comes in at around £50 because it projects its information from a smartphone, rather than a standalone screen.

What are the safety implications of a head-up display?

A head-up display puts key information in front of the driver, so they spend more time looking at what's in front of them.

In an experiment which assessed the reaction times of drivers identifying pedestrians while checking their speed (head-up and head-down units were both used), findings from a study showed HUDs presented a time advantage over head-down systems, which resulted in drivers identifying more pedestrians.

These findings would seem to suggest that buying a car with a HUD makes for safer motoring. However, critics say that it can become a distraction.

Some believe that another screen won’t help drivers keep their attention on the road. They argue that being able to shuffle through songs or see phone notifications is just another distraction.

Cars with head-up displays

A large number of manufacturers now offer a HUD, although few manufacturers fit the equipment as standard. Below is a table showing which makes and models come with the option of a HUD.