The History of Traffic Rules — 2-part series

• Part 1: Dividing the Road (this article)
• Part 2: Speaking in Light

The History of Traffic Rules Part 1: Dividing the Road — Why Britain Keeps Left and America Keeps Right

At 5 a.m. on Sunday, September 3, 1967, drivers across Sweden crossed over to the other side of the road with their hands still on the wheel. Millions of people changed a lifelong habit overnight. And they did it after a referendum in which more than eight in ten voters had said no.^[1] Switching the direction of traffic came at a real cost. So why did some countries end up driving on the left and others on the right in the first place? And why did Britain and the United States, two countries that share a language, end up as exact opposites?

How Believable Is the Sword-Hand Story?

The most famous explanation involves swords. A right-handed warrior wears his sword on his left hip and draws it with his right hand. So, the story goes, he walked on the left, keeping any oncoming stranger on his right-hand side, where he could reach him. A related version claims that Japanese samurai preferred the left side of narrow lanes to avoid the scabbards of passersby clashing, and that this is how left-hand traffic took hold in Japan.

The theory sounds plausible, but it has many weaknesses. First, there is no documentary evidence for it. Chris McManus, a scholar who has studied left- and right-handedness, notes a claim that in 1300 Pope Boniface VIII ordered pilgrims to keep to the left. He also points out that a rival claim says the pope told them to keep right, and that no record supports either version.^[2] Second, the theory assumes travelers on foot or on horseback. Rules of the road became truly necessary only once carriages and freight wagons multiplied, and what mattered then was not swords but keeping wheels from colliding. On the American side there is even a weapons story that points the other way. According to an older study cited by the U.S. Federal Highway Administration, travelers carrying rifles tucked them under the left arm and walked on the right.^[6] In other words, a weapons story can be attached to either direction.

The evidence from antiquity does not lean one way either. The roads of Pompeii, in Italy, are deeply carved with cart ruts, and the archaeologist Eric Poehler analyzed some 600 wheel-wear marks on street curbs and stepping stones. He concludes that when streets were busy enough to need lanes, Pompeian carts kept to the right.^[3] Yet a Roman quarry access road excavated in 1998 at Blunsdon Ridge, near Swindon in England, pointed the other way. Deep ruts from wagons leaving fully loaded lay on the left, and shallow ruts from empty wagons going in lay on the right. Bryn Walters of the Association for Roman Archaeology read this as evidence that Roman wagons kept to the left.^[4] Still, a single quarry road cannot tell us the rule for an entire empire. For antiquity, it is safer to assume that local custom and terrain came before any nationwide rule of the road.

One of the Earliest Recorded Rules Came from London Bridge

One of the earliest cases we can confirm in the records is London Bridge. In 1669, the City of London’s Court of Aldermen ordered that people be stationed on the narrow, crowded bridge so that carts going each way kept to one lane. The order did not say which side. In 1722, the Lord Mayor placed three men on the bridge to direct traffic, and carts entering the City from the south were to keep to the west side, while carts leaving the City kept to the east. Seen from the direction of travel, that meant everyone kept to the left.^[5] This rule was written into the London Bridge Act of 1756.^[5] It matters as an early documented case of left-hand traffic. But it applied to a single bridge in a single city. It would take nearly another century before a rule like this reached the whole country.

Why Did America Choose the Right? The Logic of the Freight Wagon

America’s right-hand traffic is closely tied to its huge freight wagons. From around 1750, the Conestoga wagon came into use around Lancaster, Pennsylvania, pulled by teams of two, four or six horses. The teamster usually rode the left rear horse, sat on a “lazy board” fitted to the left side of the wagon, or walked on the left side of the team. That meant holding the reins in the left hand and a long whip in the right. From that position, it is easiest to judge the gap between wheels if oncoming wagons pass on your left. So teamsters kept to the right side of the road. This is the explanation offered by Albert Rose, as presented by the Federal Highway Administration.^[6] The Australian road historian M. G. Lay agrees that the Conestoga wagon was the “major impetus” behind right-hand traffic in the United States.^[6]

The custom became law in 1792. According to Rose, up to that year neither the United States nor any state had set an official rule of the road. That year Pennsylvania chartered a turnpike between Lancaster and Philadelphia, and its charter included a provision that traffic should keep to the right side of the road.^[6] In 1804 New York became the first state to require right-hand traffic on all public roads, and by the time of the Civil War every state followed the right-hand rule.^[6] In the end, America’s right side was not the decision of some great man. It was built up from the know-how of people driving heavy wagons, and then written down by turnpike companies and state governments.

This explanation has its limits, of course. It does not mean that right-hand traffic began as a single event in America. It is better read as a wagon custom that gained strength in a setting where many colonies mixed the habits of different European immigrants. Rose adds that there was no reason to import Britain’s rule of the left, and that there was also some resentment of the customs of the old mother country. In the later 19th century, drivers of lighter carriages also tended to sit on the right to keep clear of the ditch.^[6] Even so, when it comes to why Britain’s former colonies chose the opposite direction from Britain, this explanation rests on the most concrete evidence we have.

Britain’s Left: When Custom Became Law

In Britain, left-hand traffic spread through a mix of the London Bridge rule and long-standing custom. What made it national law was the Highway Act of 1835. Section 78 of that act required any wagon, cart or other carriage that met another vehicle coming the other way to keep to the left, or near, side of the road, and offenders were punished.^[7] The rule later spread with British colonies and spheres of influence. Even today about 75 countries drive on the left, and together they account for roughly one third of the world’s population.^[8]

Some countries chose the left without ever being under British rule. In Japan, the practice of keeping to the left goes back to the Edo period (1603 to 1868). It was formally recognized in 1872, when the first railway was built with British technical assistance, and it was fixed in law in 1924.^[8] Japan’s case is often cited alongside the sword story, but it is worth remembering that today’s rule took shape only after railways and national institutions sorted the matter out.

The Story That Napoleon Turned Continental Europe to the Right

Napoleon’s name is attached to right-hand traffic on the European continent. The story goes like this. Before the French Revolution, aristocrats took the left side of the road and pushed peasants over to the right. After the Revolution, the nobles lowered their profile and everyone moved to the right, and Napoleon’s conquests then spread the rule across Europe.

But scholars who have searched the documents have found no records to back this up. Kincaid’s The Rule of the Road refutes, one by one, the sources the revolutionary story relies on, and in 1999 the sociologist Ian Watson concluded that the tale is a legend with no demonstrable basis in fact.^[9] The dates do not fit either. In Russia, Empress Elizabeth is said to have issued a decree in 1752 ordering right-hand traffic.^[8] That was long before Napoleon swept across Europe.

None of this means Napoleon had nothing to do with it. Several accounts say his conquests spread right-hand traffic to the Low Countries, Switzerland, Germany, Poland and parts of Spain and Italy.^[4] But that describes French practice being imposed on conquered lands. It does not explain how a direction of traffic came about in the first place. Peter Kincaid’s The Rule of the Road, the first book-length treatment of the subject, takes as its starting point that the custom reaches back well before the automobile.^[9] Lay’s conclusion, mentioned above, points the same way: there is no reason to think either side is technically better.^[6] So Napoleon may have been one factor among many, but it is safer to say he was not the decisive single cause. Continental Europe’s right side was not the order of one man. It was the result of many countries gradually converging on the same direction over a long time.

The Car Sets the Right in Stone, and Sweden Turns Late

In the 20th century, the arrival of the automobile gave right-hand traffic another boost. In 1908 Henry Ford standardized the Model T with the steering wheel on the left, and because the car sold in such large numbers, other manufacturers followed suit by around 1915.^[6] Before that, many American cars had the driver’s seat on the right even though traffic kept right. In the right-hand-traffic world, the left-hand steering wheel became the standard.

Sweden shows how this trend could fall out of step. Sweden kept left-hand traffic, yet about 90 percent of the cars on its roads had left-hand steering.^[1] That put the driver on the side of the car farthest from oncoming traffic, so head-on collisions while overtaking on narrow two-lane roads were reportedly common.^[1] Another reason was that neighbors such as Norway and Finland all drove on the right.^[1] In a 1955 referendum, 83 percent voted against switching, but in 1963 parliament decided to go ahead, and the change took effect at 5 a.m. on September 3, 1967.^[1]

The result was surprising. Right after the switch, traffic accidents dropped sharply. The analysis is that speed limits were lowered and everyone drove more carefully. Road deaths had peaked at 1,313 in both 1965 and 1966; in 1967, the year of the switch, they fell to 1,077. By 1968 and 1969, however, the toll was back up to 1,262 and 1,275.^[1] What had reduced the danger was not the right-hand direction itself but the alertness created by an unfamiliar situation. Although 83 percent had opposed the change beforehand, one survey found that 57 percent viewed it positively afterward.^[1]

Sweden was not the last to change direction. Okinawa switched from right to left at 6 a.m. on July 30, 1978, and Samoa made the same switch on September 7, 2009.^[8] Changing direction is possible, but it is a hard job because the entire country has to move at the same moment.

From Direction to Line: Making the Rule Visible

The rules up to this point were invisible. Drivers relied on habits handed down from the days of horses and carriages, and on the wording of laws, and kept to the right or left on their own. But as cars got faster and roads got wider, habit alone was no longer enough. On an unmarked road, a car coming straight at you was far more dangerous than a carriage. So the next step was to paint the rule directly onto the road.

The person most often named as the originator of the center line is Edward N. Hines of the Wayne County Road Commission in Michigan. Hines, then a commissioner, is said to have come up with the idea of a painted center line in 1911.^[10] The Michigan Department of Transportation likewise records that in 1911 the Wayne County Road Commission painted the nation’s first center line on River Road near Trenton.^[11] A story goes with it: he got the idea after seeing a leaking milk wagon leave a white trail down the middle of the road.^[10]

This anecdote deserves some caution, though. The milk wagon story is widely repeated, but it is hard to call it a fact confirmed by independent records. And even if Hines did start it, his line was one of several experiments tried in different places. The same MDOT record notes that in 1917 the Marquette-Negaunee road in Marquette County became the first state trunkline in the United States to be marked with a center line.^[11] In April of the same year in Oregon, a yellow line was painted on the Columbia River Highway on the orders of Multnomah County deputy sheriff Peter Rexford.^[10] Rather than an invention, it was a solution that occurred to many people in many places at once in the age of the automobile.

The story of June McCarroll of California belongs to this current as well. A nurse and physician, she was driving her Model T on a paved road near Indio in the fall of 1917 when an oncoming truck forced her off the road. She concluded that a white line down the middle of the road could reduce such dangers, and is said to have picked up a brush and painted one herself.^[12] After a long campaign of petitions and letters through women’s organizations, the California Highway Commission adopted the idea in November 1924, and by one account painted center lines along about 3,500 miles (about 5,600 kilometers) of road at a cost of $163,000.^[12] However, accounts differ in their details, and because earlier cases such as Hines’s exist, it remains disputed whether she can be called the first to conceive of it.^[12]

Britain saw a similar sequence of events. In 1914, a white line was painted on a dangerous bend of the London-to-Folkestone road near Ashford in Kent. In 1921, a center line was tried on an experimental basis at Maney Corner in Sutton Coldfield, near Birmingham, after residents complained about careless driving and repeated collisions. In 1926, the Ministry of Transport issued its first official guidance on where and how to use white lines.^[10] Line colors were settled differently from country to country. The United States did not standardize them nationwide until 1971: yellow for lines separating opposing traffic and white for lines separating lanes going the same way.^[10]

How an Unseen Agreement Became a Line

Seen this way, traffic direction and the center line lie along one continuous path. At first there were teamsters’ know-how and local custom. Then bridges, turnpikes and national laws turned that custom into written rules. And when the automobile raised speeds and risks, the written rule finally became paint on the road. The rule kept moving to places where it was easier to see.

For readers in the English-speaking world, the divide runs straight through the family. The United Kingdom, Ireland, Australia, New Zealand and South Africa keep left, while the United States and Canada keep right.^[8] Even that border is not an old, fixed line: British Columbia moved to the right in stages between 1920 and 1922, New Brunswick, Nova Scotia and Prince Edward Island followed in 1922, 1923 and 1924, and Newfoundland only switched in 1947.^[13] That is why an American renting a car in Edinburgh or Sydney, or a Briton picking up a rental in Florida, spends the first few days fighting muscle memory at every roundabout and turn. The rest of driving works the same in both places. What differs is only which side everyone else has agreed to use.

The question of right versus left was, in the end, never about which side is correct. It was about whether everyone picked the same side. Sweden changed direction in a single day against the wishes of most of its people, not because it did not know which direction was better, but because the cost of driving on a different side from its neighbors had become greater. Britain and America did not split because each insisted on its own road. Each simply saw the habits that had hardened first on its own wagons and roads become law. And the center line was the first solution to give that old agreement a visible shape. Yet the road still held one more problem that direction and lines alone could not solve: who goes first at an intersection.

Next: Part 2: Speaking in Light