Two years ago, the freeway interchange at the main entrance to the mountain town of Vail, Colorado, had become badly overcrowded.

The traditional solution called for $15 million worth of off-ramps, overpass widening and traffic lights—the kind of massive concrete jungle that Vail's residents moved to the mountains to leave behind. They wanted something smaller, greener, and friendlier to bicyclists and pedestrians.

In a highly controversial decision, the town council voted instead for a $2.2 million pair of modern roundabouts—one at each end of the interchange. Hundreds of these new types of intersections have been built throughout Europe, Britain and Australia in the last 15 years, but this would be the first one for Colorado. Skeptics charged that Americans could never learn to use it, that it would be a safety and traffic flow disaster, and that road-widening was the only answer.

Downtown Vail, Colorado.
Original graphic courtesy of Virtual Vail.

Well, the jury is in. After watching the new roundabouts easily handle peak ski-season rush hours in last year's snow storms, both Vail newspapers published apologies for their earlier opposition. Traffic, which used to back up onto the freeway so often that special auxiliary lanes were built to handle it, now rarely exceeds queues of six vehicles. Crashes for the fourth quarter of the year fell from an average of seven to just four, with no injuries since the completion of the roundabout.

In this story of skepticism and success lies opportunity for Palo Alto, California. In Palo Alto's Midtown, merchants and residents want to change a tired, auto-oriented strip into a people place: to add the wide sidewalks, bike lanes, street trees, landscaping and sidewalk tables needed to get people to stop, get out of their cars, and stroll and shop.

Not-so-downtown Vail, Colorado:
Interstate 70 passing through the valley.
Original graphic courtesy of Virtual Vail.

To create that neighborhood feel, that part of Middlefield Road must be downsized from four lanes to three or even two. But how to do it without creating unacceptable congestion, and diverting traffic from Middlefield onto neighborhood streets? Across Europe, and increasingly throughout the United States, the answer is plain to traffic engineers: replace Midtown's traffic light with a safer, more efficient intersection design—a modern roundabout.

In what's being called the "traffic management success story of the past decade," hundreds of modern roundabouts—smaller, slower, and much safer than old traffic circles—have been replacing traffic lights and stop signs all across Europe, and now in the U.S. too. In France, they are being implemented at the rate of about 1,000 per year. In the Netherlands, more than 400 were built between 1986 and 1992. In Norway, the number swelled from just 15 in 1980 to 500 in 1992; in Switzerland, from 19 to 220 during the same period. And now some two dozen have been built in the United States, in places from Santa Barbara, California, to Daytona Beach, Florida, and Montpelier, Vermont. They are being installed for five reasons:

Downtown Palo Alto, California.
Original graphic courtesy of the City of Palo Alto.

Safety

Because modern roundabouts require all drivers to slow, turn, and yield before entering the intersection, crash rates are 30 percent to 60 percent lower than at traffic signals. And because traffic moves at just 10-15 mph through the roundabout, accidents that do occur are much less likely to cause injury or death. When properly designed to ensure slow speeds, injuries for bicyclists and pedestrians at roundabouts sharply decline too: thus, roundabouts have become the Netherlands' design of choice for intersections used by hundreds of bicyclists and pedestrians per hour.

Capacity

Roundabouts are typically up to 30 percent more efficient than traffic signals, partly because there is no wasted green time, and partly because with traffic moving slowly through the intersection, drivers can take advantage of smaller gaps in traffic to take their turn and enter.

Not-so-downtown Palo Alto, California:  the campus
of Stanford University, adjacent to Palo Alto.
Original graphic courtesy of Stanford University.

To Avoid Widening Roads, or to Downsize a Street

Four lane roads are often needed for just one reason: to provide a place to stack up cars waiting at the red light. But modern roundabouts distribute the queues evenly around all four sides of the intersections, so that extra storage lanes aren't needed. As Santa Barbara traffic engineer Leif Ourston puts it, "Two lanes moving all the time have roughly the same capacity as four lanes stopped half the time at red lights."

Cost

On average, traffic signals require $3,000 per year in electricity, bulb replacement and other maintenance. Roundabouts, by contrast, offer far lower maintenance costs. And the gains from avoiding major road widenings can, as at Vail, run into the millions.

Environmental Benefits

Because roundabouts involve less delay, they can also reduce air pollution from idling vehicles. They're quieter, because of lower speeds and reduced braking and acceleration noise. By getting rid of the 'expressway' look and feel of many arterials, they help reduce speeding nearby. And the landscaped central circle offers the chance to create more beauty, and more of a landmark for Midtown, than the blank asphalt of a traffic signal.

Pedestrian and bike traffic, not too far removed from vehicle traffic, could
move more safely through Palo Alto with the aid of modern roundabouts.
Original raphic courtesy of City of Palo Alto.

Thirty years ago, Palo Alto was in the face of widespread skepticism as one of the first cities in the nation to build bike lanes, and since then we have reaped large benefits in safety, community and livability. Now we have the chance to do the same with modern roundabouts. So I wonder:  Is the town where I grew up biking still ready to lead the way in building better, safer neighborhoods? I think so.