Golden will look to slow lead-footed drivers on its residential streets, with the launch Tuesday evening of an effort to slice 5 mph off the speed limit on the city’s smaller neighborhood streets.
The city council moved the item along Tuesday night with a showing of thumbs-up, pledging to formally take up the issue for a vote in the coming weeks. Full implementation likely wouldn’t occur until the fall.
“The idea of trying to reduce this thing to 20 (mph) is a real benefit to the safety of the public,” Councilman Paul Haseman said.
Golden, should it move ahead with the idea, would be following in the footsteps of Denver and Boulder, two metro area cities that have in recent years put in place a 20 mph limit on neighborhood streets — 5 mph below the typical 25 mph limit.
Aspen made the move nearly a decade ago and there are an increasing number of cities across the nation — including Madison, Wis., Eugene, Ore. and Norfolk, Va. — that have adopted the lower residential speed threshold.
But according to a report completed in March by Boulder analyzing its own “Twenty is Plenty” program, which it launched in June 2020, the city found that motorists did not slow down on neighborhood streets after the speed limit was lowered.
In fact, the average speed on those streets, as measured by the city at 22 different locations before and after, actually rose slightly from speeds recorded before the new signs were mounted — 21.57 mph before versus 21.9 mph after. And the share of motorists driving slower than 20 mph on Boulder’s local roads, the report said, dropped from 39% before the campaign to 33% after.
“The City found that, overall, vehicle speeds on local streets did not measurably change after implementing “20 is Plenty,” the report concluded. It found that Portland, Ore., which has also cut its local street speeds from 25 mph to 20 mph, did not see a reduction in motorists’ speeds either.
Devin Joslin, Boulder’s principal traffic engineer, said it’s likely that Twenty is Plenty is not sufficient by itself to alter driver behavior. Redesigning roads to slow down traffic, which could include narrowing streets or installing traffic-calming measures, need to play a role too.
“This is one part of a broader process to change driver behavior,” Joslin said.
The National Transportation Safety Board considers 20 mph the “survivability speed” for pedestrians and bicyclists when involved in a crash with a vehicle. For pedestrians, the
probability of a crash being fatal at an impact speed of 20 mph climbs from 5% to 45% when that speed rises to 30 mph. The fatality rate at 40 mph jumps to 85%.
The group 20’s Plenty for Us, based in the United Kingdom, claims that crash data show 50% of all pedestrian fatalities and 80% of serious injuries occur with vehicles moving between 21 mph and 30 mph, but “only rarely at 20 mph and lower.”
According to an analysis released by AAA Colorado last year, the number of pedestrians killed annually on Colorado’s roadways has nearly doubled since 2009. The Colorado increase surpasses a 55% nationwide rise in pedestrian deaths over the same period.
From 2009 to 2018, pedestrian fatalities in the U.S. rose from 4,109 to 6,374, according to the AAA report. In 2009 and 2010, there were 47 and 36 pedestrian deaths respectively in Colorado. In 2017 and 2018, the numbers were 92 and 89.
“The motivation behind the change is to reduce serious injury outcomes on our streets,” Joslin said. “It is a first step and a call to action for the public.”
Boulder, he said, spent $65,000 to $70,000 replacing nearly 500 speed limit signs, and another $55,000 to pay for the study to measure its performance.
Denver passed its Twenty is Plenty initiative in December and hasn’t had time to fully roll it out. It will start by swapping out or removing speed limit signs so that drivers know there’s a new, lower limit in effect.
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“To implement this proposal, we’ll be addressing 2,700 to 3,500 25-mph speed limit signs currently placed on local streets,” said Nancy Kuhn, spokeswoman with Denver’s Department of Transportation and Infrastructure. “We anticipate that removing and replacing these signs will take three to five years to implement from the time we begin.”
Despite the less than stellar data out of Boulder and Portland in terms of the program’s success in slowing drivers down, Kuhn said the city still regularly hears concerns from residents about vehicles speeding through neighborhoods.
“We hope reducing the speed limit on our local streets will address resident concerns,” she said. “We also think the initiative could draw attention to the topic of speed in general — get people thinking about it and about driving the speed limit.”
Golden Councilman Don Cameron, the main sponsor of the measure, said the Twenty is Plenty concept is generally popular where it is introduced.
“There should be pretty good buy-in,” he said of his constituents Tuesday.