This guide will ensure you're safe and seen on the roads. They light the way at night, help you indicate when turning and warn other drivers of your presence in poor conditions - your car lights are vital to staying safe on the road. But if a bulb blows, do you know how to change it? Follow this guide and you'll not only save money, but also stay legal and safe while driving.

When a bulb blows

Unless you check your lights on a regular basis you won't notice something's amiss until other drivers flash their lights at you. Thankfully bulbs don't fail all that often, but when they do, it tends to be the lights that do the most work - like a brake light. A blown bulb is not only a safety issue - it will cost you at MOT time, not to mention the fact it's illegal. If you're caught without a working car light, you could be on the receiving end of three points and higher car insurance premiums.

Check what the problem is

If one or more of your lights aren't working, make a few checks before you start taking the car apart as it may not be the bulb that's the problem: • Is the switch working properly and in the correct position? • Are the other electrics working OK? Check the handbook for further information that's specific to your car.

Will any old bulb do?

No! There's a vast range of sizes, shapes and types of bulbs available, so make sure you get the right one for your car. Check the handbook for the exact specification, or better yet, extract the old bulb and take it with you to the shop. Headlights are more expensive than backlights and upmarket cars tend to use halogen or xenon bulbs, which aren't cheap to replace. But don't skimp on the cost. Purchasing and fitting them yourself, rather than going to your dealer, will save you money.

How to fit your new bulb

Backlights

Changing a bulb isn't always straightforward, but if it's a rear bulb that's blown, it's not too bad. Open the boot and remove the plastic or fabric cover over the innards of the lights. Look closely at the replacement - this will show you how it fits (screw-type, bayonet or other) - so you can remove the old one. Do this slowly and carefully. You don't want to damage any of the connections or break the bulb. Once the new bulb is in, check it works before putting it all back together.

Headlights

Modern cars tend to be crowded under the bonnet. This means you have less space to work with. Getting behind the headlight is often less straightforward but here we will take you through the steps:

Step one: Tools

Have a small selection of tools on hand. Pliers, screwdrivers and a socket set will be a big help.

Step two: Research

Look in your handbook, give your dealer a ring, look online or consult a workshop manual for advice - there may be a trick to getting access to the bulb that's not immediately obvious. For example, the last-generation Mondeo requires you to whip off the grille first then release a bolt so the whole headlamp unit swings out.

Step three: Patience

Changing a bulb is one of those jobs you think should take five minutes, so if you're still there an hour later it's easy to get frustrated. Allow yourself plenty of time - your safety, and the safety of your passengers, is at stake.