Sunday, June 12, 2016

Napa Valley Register: Roundabouts are coming, but do they work?

On key Napa-area roads, the shape of things to come may be a circle.
City and state officials are moving toward replacing a set of busy intersections with a trio of roundabouts to link Highway 29 with downtown Napa. Engineers have offered another circular hub – or two – to replace a convoluted five-way junction on the east end of town. Even outside the city limits, a planned high-speed connection between Highways 29 and 221 could see a towering flyover ramp replaced by yet another pair of roundabouts.
Virtually unknown in the U.S. a quarter century ago, the stoplight-free junctions – widely used on British and French highways for decades – have gradually appeared in California and other states, as its supporters have embraced the design as a boon to safety, traffic flow and air quality. But even as Napa County draws nearer to seeing its first examples of the design, local planners say the first step to getting drivers to accept roundabouts is to educate them about what they are not.
“The Arc de Triomphe? Not a roundabout. A big high-speed rotary in New Jersey? Not a roundabout,” said Ross Ainsworth, describing the slide-show pitch that, Omni-Means Ltd. of Roseville, the transportation design company of which he is president, delivers when bringing roundabout plans to new, and sometimes, skeptical communities.
Despite such misconceptions, the firm is pressing forward with designs that would eliminate traffic signals and full stops at congested crossings on California Boulevard and the Silverado Trail. The new-style junctions, if built, would join a growing number of intersections moving away from the sharp-angled mainstream.
From the earliest American roundabout created in Summerlin, Nevada in 1990, the carousel-like crossings have slowly spread across the country, with estimates on the nationwide number ranging from 3,500 to 5,000. California may be home to about 300 roundabouts, though that number likely includes older crossings without all the features of newer connections, according to Jerry Champa, a liaison for Caltrans traffic operations.
The Federal Highway Administration describes the modern roundabout as a counterclockwise hub designed to keep motor vehicles moving slowly, but always moving, usually at 15 to 25 mph: faster than neighborhood traffic circles, but slower than the wide-radius rotaries seen in parts of the Northeast.
In place of stoplights and stop signs, drivers entering roundabouts face yield signs requiring them to give way to those already within the hub. All turns are right-hand turns; a driver who would turn left at a normal intersection instead completes a three-quarter revolution before taking the third cross street on the right.
The real value of roundabouts lies in their ability to turn potentially deadly or devastating broadside strikes into slower and less dangerous fender-benders, according to Eugene Russell, a civil engineering professor at Kansas State University and a longtime advocate of the design.
Even as death rates on U.S. roads have generally gone down over the years, “the one thing that’s stayed about the same is intersection fatalities, which have been constant at about 20 to 25 percent of the total,” Russell said. “That’s a large chunk of our highway deaths annually. This is why I promote roundabouts.”
Largely by eliminating left turns, roundabouts reduce the rate of crashes causing death or serious injury by 78 to 82 percent, compared to crossings governed by signals or stop signs, according to Federal Highway Administration.
Starting in the early 2000s, California began requiring cities and counties to consider roundabouts as one option for any state highway intersection where traffic lights are proposed, records show. The state expanded its mandate in 2013 to projects involving reconstruction, widening or interchange fixes.
Besides lowering accident rates, a circular pattern requires less pavement and fewer lanes for the same amount of traffic, while reducing the stop-and-go driving that produces the heaviest vehicle emissions, according to Champa of Caltrans.
In Napa, city engineers warmed to the idea of junking stoplights on California, First and Second near Highway 29 after deciding a set of roundabouts would eliminate the need for a costlier and more radical road surgery – building a replacement for the narrow and curving First Street flyover across the freeway, according to Eric Whan, deputy public works director. Such an overhaul, Whan estimated, would require $40 million to $50 million and have to compete for funding with other plans to upgrade the highway in south Napa or near the county airport.
“The idea was to really fix the issues with traffic on First Street at the (freeway) interchange,” he said. “Without (roundabouts), you would have had to rebuild the whole interchange, and with all the other needs in the county, it probably would have never gotten done. There’s no funding to do all of that work in the near term.”
Despite roundabouts’ rising profile, the experience of Calistoga shows that not all audiences can be convinced – and not all ill-designed junctions can be transformed into sleek traffic pipes.
A four-way intersection where two-lane Highway 29 awkwardly bisects the right angle formed by the Silverado Trail and Lake Street became the focus of a planned circular hub. Engineers hoped to use a roundabout, estimated to cost at least $3 million, to unkink a notoriously crooked street plan that had contributed to several serious wrecks.
The hub, however, never arrived, and Caltrans in 2012 pulled the plan off its list of active projects. While the city at the time cited the cost and staff time needed to compile project documents, Calistoga’s mayor recently conceded residents simply were not ready for the change.
“There was zero community support, to the point of assertive community opposition to it,” recalled Chris Canning, the mayor since 2010. “We had to go back to Caltrans and the (Napa Valley Transportation Authority) and say ‘Sorry, but as a city we can’t support it.’ I’m from New England and I’m used to roundabouts that are very efficient at what they do, but I can understand why people would find them a little bit scary.”
Even with the buy-in of local drivers, development had encroached too close to the crossing for a roundabout to be practical, Canning added. Land takings would have effectively cut off access to La Prima Pizza restaurant or forced its move, he said of the junction, which received stop signs in all directions several years ago to reduce the collision risk.
In Napa, the plan to build roundabouts west of downtown gained the City Council’s approval in May — but not the support of bicycling enthusiasts, who worried the design could expose cyclists to greater risks. Two-lane sections in particular would leave those on bikes vulnerable to sudden lane changes by drivers unfamiliar with roundabouts, said Patrick Band, executive director of the Napa County Bicycle Coalition.
(Public works officials have said the more consistent traffic speed within roundabouts would create safer conditions for all users, and the city also is seeking funds to build a pedestrian east-west path below Highway 29, north of First Street.)
A roundabout makeover in Minnesota may point the way toward improving safety, even at a crossing with multiple lanes in play.
After an increase in minor but frequent crashes at a crossing that became a double-lane hub in 2011, a transportation laboratory based at the University of Minnesota added signs and lowered them to eye level, extended solid white lines and made other tweaks. Lane-change violations fell by 20 percent and turning infractions by 40 percent after the changes, according to the Roadway Safety Institute newsletter.
Ainsworth, of Omni-Means, expressed confidence that roundabouts, though still the exception, will become closer to the norm in Napa and elsewhere. “Once the public observes them, once it has an opportunity to use them, they come to understand firsthand what the benefits are,” he said.

(Source: http://napavalleyregister.com/news/local/roundabouts-are-coming-but-do-they-work/article_1bcfc39a-4309-5b2a-9df7-f85fe2c081ed.html)

No comments:

Post a Comment