I decided to hire a car for my second weekend in South Korea, as the locations I wanted to get to were too far apart to conveniently string together using public transport. The driving wasn't difficult for the most part, but there are a couple of caveats foreigners should be aware of. The first and most important requirement is an International Driving Permit (IDP). Foreign driving licenses, regardless of country, are not accepted in South Korea. Local motoring organisations around the would can supply an IDP for a nominal fee; in Ireland, this cost me €15 through the AA. There are two different types of IDP available, each of which covers different countries, so be sure to check that you've ordered the right one.
The next trick is choosing a supplier. Hertz offers rental cars in Korea, but their services are franchised through the local company, which is KT Kumho. These offices can be difficult to find; for example, the one at Daejeon Station is almost five minutes walk from the station exit, and it is not signposted. Furthermore, the Hertz logo in the window is small and could easily be missed. I programmed my GPS with exact coordinates for the office before my trip.
There are free GPS maps for Korea (and many other countries) available from OpenStreetMap, and these are fairly good. The road locations are almost perfect, but some of the routing can be more than a little strange; at one point, for example, I was instructed to leave a motorway then drive straight back onto it. Furthermore, the waypoint information is next to useless due to ambiguities in spelling. For best results, I'd recommend having exact coordinates for all intended destinations sourced from Google Earth, backed up by a sanity check after programming to make sure that your locations are where you expect them to be.
The staff at KT Kumho may or may not speak English, but if they don't they will phone their head office where someone else can translate for them. In addition to all the normal details required for a car rental, they ask for a national ID number as well as hotel details (including room number). Be patient and allow lots of time; in my case the rental process took almost an hour. All paperwork was reviewed and signed on an tablet computer rather than in hard copy.
Koreans drive on the right hand side of the road, and all rental cars in the country have an automatic transmission. My car today was a Kia K3, best described as a gadget lovers dream. It had heated seats, a heated steering wheel, folding wing mirrors, automatic lights, and parking sensors. It was also very comfortable and pleasant to drive, despite the fact that it didn't have cruise control.
City driving in Korea is challenging, mainly because many of the roads are narrow and there are parked cars everywhere, often blocking at least half of the travel lane. Right turn on red is legal and expected; if you are in the right hand lane and have your indicator on, then you need to move or the car behind you will honk. Everything becomes easy outside the cities; the motorways are excellent and well maintained, and the traffic is for the most part light. Much of the network uses a ticket based tolling system where you pay the total amount on exit, but be ready for a small number of points where you need to pay then and there. Speed limits are clearly posted, and range between 80km/h and 110km/h. There are regular speed cameras, but all come with an advance warning about half a kilometre in front indicating Police Enforcement. Despite these, you will see the occasional lunatic driving at fifty over the limit down the hard shoulder, as the cameras don't seem to point there.
Refuelling can be a little tricky, as all the pumps seem to have touch screen controls in Hangeul only. Other drivers are more than willing to help, however, so you shouldn't have any major problems. Filling my rental from almost empty (with warning light on) cost just under fifty euro.
One final (and important) warning; you should allow lots of extra time to drive into the city to return your rental car. In my case, the five kilometres from the outside of Daejeon to the main station took me almost an hour on a Sunday afternoon, the last fifteen minutes of that with the train station in sight. Goodness knows how long it would have taken at rush hour on a weekday.