Every year, the Portland Bureau of Transportation (PBOT) makes improvements on Portland streets to make them safer. Some of this work has been tried and tested before. Some are newer innovations. Below are key takeaways and a series of evaluation reports on various projects, organized by type:
Roadway reorganizations
PBOT reorganizes roads by changing lane configurations, restriping, and/or building new safety infrastructure. Fewer lanes and shorter crossings make it safer and easier for pedestrians and people biking to cross. Roadway space can also be repurposed to add or improve bike lanes, a center turn lane, add on-street parking, bus platforms, plant trees, treat storm water, build new sidewalks or widen existing ones, as well as a number of other uses depending on the project.
The evaluations show that when PBOT repurposes a vehicle travel lane for other uses, travel speeds tend to go down. We also see a dramatic decrease in top-end speeding (10 mph or more over the speed limit). The projects evaluated here have had minimal impact to travel time, transit reliability, or overflow traffic spilling into nearby residential streets.
Roadway reorganization evaluation reports (from newest to oldest):
Speed limit reduction
Setting safe speed limits has a number of important benefits aside from legally requiring people to drive slower. Consistent safe speeds limits result in lower driving speeds, promote a culture of driving slower, and allow us to design streets for slower speeds.
The evaluations from Portland and other cities we've included here show how reducing the speed limit resulted in lower observed speeds and a more pronounced decrease in drivers travelling at high speeds.
Speed reduction evaluation reports (from newest to oldest):
Lowering the speed limit from 30 to 25 mph in Boston: effects on vehicle speeds (2020) - from IIHS
Quick-build interventions
To address the many needs across the city more quickly, PBOT is consistently exploring small and cheap interventions we can build in multiple locations to address the common causes of crashes.
Left-turn calming is one intervention that PBOT piloted in 2019 to help protect pedestrians. Hardening the centerline at certain intersections by adding rubber speed bumps or plastic or concrete barriers led to people slowing down while making left turns and substantially reduced the number of sharp, angled turns.
Quick-build intervention evaluation reports (from newest to oldest):
Other evaluation reports from Portland and other places
"After controlling for direction, hourly traffic flow, and the behavior of the vehicle (i.e., free-flowing or stopped at a red light), we found that the effect of the delineator-protected bicycle lane (marked with traffic cones and plastic delineators) was associated with a 28 % reduction in average maximum speeds and a 21 % decrease in average speeds for vehicles turning right. For those going straight, a smaller reduction of up to 8 % was observed. Traffic moving perpendicular to the bicycle lane experienced no decrease in speeds. Painted-only bike lanes were also associated with a small speed reduction of 11–15 %, but solely for vehicles turning right."
Study from Cedar Rapids Iowa showing no meaningful difference to emergency response time after implementing 4-to-3 lane conversions, despite up to 40% of EMS survey respondents saying the lane conversion had a negative impact.