Even though 66 percent of the world’s population lives in countries that drive on the right side of the road, and the remaining 34 percent live in countries that drive on the left side of the road, there’s surprisingly little interface between the two modes. This is a result of the clustering of the two styles into particular geographic regions. Left-driving countries are generally restricted to the British Isles, the Caribbean, southern and eastern Africa, the Indian subcontinent, Japan, Southeast Asia, and Oceania.
Right-driving countries are in red; left-driving countries are in blue.
Generally, left-driving countries are isolated from right-driving countries by water, mountains, desert, or large stretches of deep forest. While this provides for relatively little traffic crossover between the two mode, there are still numerous roads (about 86 or so, according to this KMZ file) where the issue of having to exchange lanes due to crossing over a border exist. These occur mostly in Africa and Asia, along with a handful of roads leading out of Guyana and Suriname in South America. To ease the transition for drivers so that they don’t suddenly find themselves hurtling headlong into oncoming traffic, there are a number of ways of handling the issue, as shown by the various roads listed below.
1. Build a one-way connector road
The crossing from Namibia’s Omusati region to Angola’s province of Cunene works this way. The border post is on the Namibian side; cars enters through customs on the left and upon leaving immediately hit an intersection with a two-way street that forces them to the right side of the road if heading through to Angola. A similar situation occurs at Sha Tau Kok, the easternmost crossing between Hong Kong and mainland China. Vehicles heading into Shenzhen from Hong Kong enter a giant control point for processing; when they are released, they depart via a one-way road which immediately leads into an intersection with a Shenzhen street.
At this border crossing between Konkola, Zambia and Kasumbalesa, DR Congo, Zambian traffic travelling on the left exits off the highway via a one-way road into customs, and then is expunged via another one-way road into the Congo, merging into right-side traffic. Notice the huge 2 km-plus wait at the border on the Zambian side.
2. Create a controlled intersection
Intersecting lanes with traffic lights are the method of choice in and around Thailand, a left-hand-drive country surrounded by right-driving Burma (Myanmar), Laos, and Cambodia.
At the north end of the Thai-Lao Friendship Bridge in the Lao capital of Vientiane, a grass median splits the two directions of traffic, which then proceed to intersect each other after a short distance, essentially creating an intersection between two one-way streets and completing the crossover:
Since this first Thai-Lao Friendship Bridge was built in 1994, two more such bridges have been constructed across the Mekong River that separates much of the two countries. All use the same intersecting crossover technique, with the crossovers on the secondand third bridges occurring on the Thai side. A fourth bridge has also been approved for construction.
Thailand also has two ‘friendship bridges’ with Burma (Myanmar). Just before the bridge at Mae Sot, we can see a crossover point where the opposite lanes of the motorway merge for a short distance to form a crossover point (an incoming road also merges into traffic at this purposely-created bottleneck):
The major Namibia/Angola border crossing at Oshikango/Kuroka (Santa Clara) doesn’t have traffic lights. Instead, it uses the customs post as an intersection. When heading north into Angola, the customs building sits in the median. Immediately north of Namibian customs, each car heading north into Angola switches into the right-hand lane to access Angolan customs (which also lies in the median).
3. Install a roundabout
A variation on the one-way intersection crossover is the roundabout, where vehicles enter the traffic circle on one side of the road and leave on the other.
Poipet is a booming Cambodian border town that caters to Thai tourists looking to gamble, as gaming is banned in Thailand. Between Thai customs to the west and Cambodian customs to the east lie a strip of casino resorts, positioned so as to allow Thai tourists to visit them without having to visit customs or change sides of the road. For anyone proceeding beyond the casino strip, the roundabout in the bottom right corner of the map below separates Thai traffic from Cambodian traffic.
Drivers leaving Man Kam To are sent into this roundabout under a freeway when leaving customs.
4. Build a crossover bridge
In high traffic crossings where lanes of traffic have to be transferred to the other side as efficiently as possible, or where a crossing is already elevated above ground due to the presence of a bridge, a crossover bridge is a handy solution. In these cases, one lane breaks from the roadway, bridges over top of the other, and ends up on the other side of the road.
An archetypal example is the Hong Kong-Shenzhen Western Corridor, built in 2005. Here, Hong Kong-bound traffic leaving Shenzhen customs on the right-hand side drives over top of the northbound lane, ending up on the left-hand side of the Shenzhen Bay Bridge to conform with Hong Kong road rules.
The most spectacular crossover bridge may be the six-lane Lotus Bridge joining Macau to mainland China via Hengqin Island. Drivers leaving Macau driving on the right cross over the bridge only to find the bridge splits in half on the other side, with their left-hand lane performing a 360-degree double back under the bridge to the right-hand side before entering customs. Drivers leaving mainland China on the right double back under the bridge and then over the inbound lane from Macau to end up on the left.
Perhaps less spectacular but more intricate is the Lok Ma Chau/Huanggang crossing between Hong Kong and Shenzhen, when four separate right-hand-drive streets are merged into the left-hand-drive side of the bridge via merging lanes.
One of the newest examples of a crossover bridge does not come from China, but rather the Guyanese-Brazilian border. The two-lane Takutu River Bridge was opened in April 2009 between Lethem, Guyana and Bonfim, Roraima, Brazil, finally joining the countries directly by road at a cost of $10 million. The crossover does not occur on the bridge, however, but on land a few hundred metres into Guyana, where the road divides so that the right-hand lane can arc over the left-hand lane similar to a rail overpass.
5. Do nothing
This is actually the most common option, thanks to most of these types of crossings being in low-traffic areas in poorer countries. For the most part, drivers simply pull into customs and, once finished, make sure to leave on the other side of the road. Signs will usually be posted reminding you to do so.
A unique situation occurs with vehicles using the Channel Tunnel joining England and France in that each side of the tunnel uses a different method of integrating drivers onto the proper side of the road. This method can be considered cheating in a way, since it doesn’t involve the physical changing of lanes in a continuous drive but rather cars driving onto a train which deposits them in a new country to resume their drive, but it is a drive-on/drive-off situation. Cars entering the train via a right-hand drive lane in Pas-de-Calais exit the train in Kent via a one-way left-hand-drive lane 35 minutes later with signs at the first intersections reminding them to drive on the left. Cars exiting in France, however, make use of a rather large roundabout to enter right-side traffic on the Continent.
A Kentish sign on top; the French roundabout on bottom with the one-way road from the tunnel approaching from the south.
Lucas, B. (2011). Which side of the road do they drive on? Available at http://brianlucas.ca/roadside/. Accessed 18 December 2011.