Study: “Shared Space” Slows Drivers While Letting Traffic Move Efficiently

The idea behind “shared space” street design is that less can be more. By ditching signage, traffic lights, and the grade separation between sidewalk and roadbed, the shared space approach calms traffic and heightens communication between drivers, pedestrians, and cyclists. Instead of following traffic signals on auto-pilot or speeding up to beat the light, motorists have to pay attention to their surroundings.

A "shared space" in Austria. Image: Transportation Research Board
A shared space in Graz, Austria. Image: Transportation Research Board

Shared space design has been shown to calm vehicle traffic and allow more freedom of movement for pedestrians with no increase in traffic injuries. A new study from professor Norman Garrick and Benjamin Wargo at the University of Connecticut finds that in the right conditions shared space also makes intersections more efficient for both pedestrians and motorists.

The study examined six sites around the world that have some degree of “shared space” and where each approach to the intersection has one lane of motor vehicle traffic. Because of the limited number of shared space designs in the U.S., only one American example is included: Uptown Circle in Normal, Illinois.

Using video, the researchers measured driver speeds and pedestrian and vehicle delay. The authors then compared those observations to computer-simulated estimates of how much delay would occur if the streets were designed with more conventional traffic control measures, like stoplights or roundabouts.

They found that in this context, shared space design calmed traffic while also creating less delay for both pedestrians and motorists than traffic signals.

A "shared space" in Normal, Illinois. Image: TRB
Uptown Circle Normal, Illinois, has fewer shared space traits than other intersections in the study, and also had higher vehicle speeds. Still, the average speed was just 10 mph. Image: TRB

The more “shared space” characteristics in the design, the calmer the traffic. For example, Sonnenfelsplatz, in Graz, Austria, where the distinction between driver and pedestrian space is blurred the most, is where motorists drove the slowest (5 mph). That site has no curbs or crosswalks. Drivers moved fastest (close to 10 mph) in Normal, Illinois’s Uptown Circle, which has painted crosswalks and a low level of “integration” between space for drivers and pedestrians.

At the same time, the researchers found that, compared to signalized intersections, shared spaces allow for more efficient movement of both people and cars.

“The pedestrians at the shared spaces showed little or no hesitation before crossing,” the authors wrote. On average, pedestrians waited less than a second to cross at all six intersections. If the intersections were signalized, pedestrians would have waited an average of 10.7 seconds, according to the simulation.

Motorists also spent less time immobilized than they would at conventional intersections. The shared spaces delayed drivers between 56 and 207 seconds less than a four-way stop would have, according to the simulation. Even compared to traditional roundabouts, the authors found that shared spaces would result in less delay if there are both a large number of people and a large number of vehicles moving through the intersection.

“The big takeaway is that shared space seems to be much, much more efficient,” Garrick told Streetsblog. “Especially when there are a lot of pedestrians around.”

16 thoughts on Study: “Shared Space” Slows Drivers While Letting Traffic Move Efficiently

  1. Shared space can work but only in very specific situations. It is not at all a panacea. Note that almost every shared space in The Netherlands, including all but one of Hans Monderman’s, has been put back to traditional Dutch design with separate and often protected bikeways, walkways, and crossings.

    Exhibition Road (Hamiton-Baillie’s Folly) in London was supposed to be a great example but today nobody in their right mind will dare walk anywhere but the sidewalks for fear of being killed by speeding cars.

    In all of these cases the shared space worked for a brief period when it was new and drivers were trying to figure it out. Once it was no longer new drivers began driving faster and faster through the space. This has been particularly a problem for blind folks and people with other disabilities.


    An example where it mostly works:

  2. Chicago’s Uptown neighborhood is soon to have the city’s first “shared street”, off Argyle and Broadway. It’s shaping up to be pretty cool, the community in this area is predominately Asian (mostly Vietnamese, specifically people who fled to Chicago after the Fall of Saigon in 1975) and there are a lot of Asian markets/restaurants/shops along Argyle Street.

  3. Yup, in the article, the key bit is

    in the right conditions

    If you want to see it in action here in the US, many suburban residential streets are effectively ‘shared space.’ Many don’t even have sidewalks or stop signs at intersections. It works in these low to medium density environments pretty well; joggers, bicyclists, kids, and cars seem to coexist pretty well there.

  4. US suburban residential streets mainly work by excluding pedestrians. I have literally been pulled over by a policeman for walking (going 6 blocks from a friend’s house to a store to pick up some lunch fixings) in a no-sidewalks quiet residential neighborhood. So few people walk that IT LOOKED CRIMINAL to him.

    They are open wastelands with manicured grass and nothing moving except cars (and the occasional dogwalker).

  5. You’ve already said it so I don’t have to. Too many people misunderstand what is necessary for a successful shared space: removal of through motor traffic. As long as the area that forms the shared space is still also a great way for motor traffic to go, it’ll just continue to be car-centric with angry drivers.

  6. I’ve brought this up before in other discussions, but it’s an important consideration because it’s so sobering. Regarding Exhibition Road in London, the following observation was made:

    “if vehicle flows are greater than 100 per hour, pedestrians will not use the vehicle zone as a shared space”

    So only 1-2 vehicles per minute. Any more and the cars and trucks bully everyone else to the sides. Now that doesn’t mean that some of the shared space design principles can’t be applied in higher volume scenarios. They can potentially be safer for all users and less expensive to build and maintain while also being more attractive. That’s certainly a win, but it just won’t be truly shared space, more like significant traffic calming.

  7. In any of the sidewalkless suburbs I’ve walked in, that would be taken down by police. So yes, it really varies. I’ve recently been in Skokie and parts of Schaumburg and Elmhurst and Lombard, and they’re all blasted no-walker wastelands.

    Cars actually honked at me in Skokie for walking in the street as close to the curb as I could manage WHEN THERE WERE NO SIDEWALKS in a completely residential neighborhood, because it was soppy with rain and I didn’t want to get my shoes muddy in the grass. The street was easily wide enough for two parking lanes and two traffic lanes (with only the one car and me present), but this guy had to get up my butt and honk at me for daring to walk in the street. With a white coat on. In daylight.

  8. He followed me, at a crawl, in his car all the way back to my friend’s house and insisted on accompanying me up the front driveway and ringing the doorbell to be sure they knew who I was. Over the top and ridiculous.

  9. That sounds terrible! I haven’t been in the heartland much, but along the coasts at least I’ve seen something closer to the street I posted in most places.

  10. As @marvennorman:disqus pointed out below, It’s much more than volume. People driving to a local destination drive slower and more cautiously, people driving through an area on their way somewhere else will usually drive faster and less cautious — they just want to get where they’re going… Quickly.

    What Dutch engineers have learned is that it’s also more than a singular volume number but a relative number. A space can only be shared so long as bicycle riders outnumber automobiles by at least 2:1 and ideally 4:1.

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