Luckily there aren’t many countries that drive on the opposite side of the road and share borders. However, they do exist, such as China, which drives on the right, and the former British colony of Hong Kong, and former Portuguese colony of Macau, both which drive on the left. This can pose an interesting problem for engineers and road planners, but Dutch architectural firm, NL Architects, has come up with a bridge with a twist – a concept that not only puts the drivers on the correct side of the road physically, but helps reinforce that fact visually to help get the drivers into the mindset of driving on the opposite side of the road.

Left or right?

The grooves of a well-preserved track leading to a Roman quarry near Swindon, England, suggests that Romans drove on the left. It has been theorized that riders on horseback generally rode on the left so they could hold their reigns with their left and keep their dominant hand free to offer a greeting to passing riders or to defend themselves with a sword.

In the late 1700s in the U.S. teamsters driving large freight wagons pulled by several teams of horses were positioned on the left rear horse so they could hold the whip with their right. To ensure the clearance of the wheels of oncoming wagons they preferred that wagons pass them on the left where they had a better view. This prompted a shift from left to right-hand traffic in many countries. So much so that today around two thirds of the world’s people live in right-hand drive countries.

Current bridges

Hong Kong and Macau have retained left-hand traffic after returning to Chinese control in 1997 and 1999 respectively. There are already some interesting solutions to the problem of setting drivers on the right track when crossing the border such as the Lok Ma Chau bridge between Hong Kong and mainland China, and the Lotus Bridge between Macau and mainland China. Although both these solutions get the job done, they don’t really communicate visually to the driver what is happening.

The Flipper

Dubbed “the Flipper” by its designers, the Pearl River Necklace bridge concept features the different sides of the road separating and twisting around each other to meet up on the opposite side. Unfortunately it doesn’t look like we’ll be seeing the concept become a reality. NL Architects designed the bridge as part of a competition, but lost – possibly because the switchover technically took place in the wrong location.