In Barbados you'll drive on the left as you do in the UK. Most of the roads are in very good condition but watch out for potholes when you get out into the countryside. The most pressing danger to watch out for is when driving at night. Many roads do not have pavements and so pedestrians usually walk on the side of the road where they may be difficult to see.
Roads are generally quite narrow and busy apart from the ABC highway. Also watch out for the buses and vans, they go much faster than you might expect. Having a map or a GPS is invaluable. Although Barbados is very small it is very easy to get lost, especially if you follow local instructions! If a driver flashes his headlights at you at an intersection this means that you can go ahead. Because of the potential for car theft, you should never leave valuables in an unattended vehicle and always park in well lit areas. You are advised never to pick up hitchhikers.