♫ music ♫
[wind noise]
Traffic in this Washington State interchange flows like clockwork
thanks to three unique roundabouts.
It wasn't always this safe and efficient.
The intersection of Slater Road and Interstate 5
had increasing problems with traffic backup.
Dina Swires: "Level of service was 'F.' They were failing.
We had people backing up on mainline.
They were going 70 on the interstate.
They didn't know what to do. Whatcom County had to do something."
A team of transportation professionals used a novel approach
called Data-Driven Safety Analysis to solve the complicated
traffic problem and justify their decisions.
Data-Driven Safety Analysis is the application of the latest generation of tools
for analyzing crash and roadway data.
These tools quantify safety impacts, so agencies can make more informed decisions,
better target their investments,
and reduce severe crashes on the roadways.
The team analyzed each intersection, and decided that a series of compact roundabouts would
provide the best level of service and benefit cost.
Dina Swires: "Highway Safety Manual applications gave us the encouragement
to show that we wouldn't compromise safety and still gain the
amazing safety benefits that roundabouts afford.
So, we suggested, 'Let's put a compact in the existing right of way.'"
For the project to work within budget constraints,
the team had to take a flexible approach to the design.
"So, we started doing things like taking out the outside curbing.
Drainage was easier and less expensive.
Then we started playing with the size of the roundabout."
[car passing]
A speed study confirmed that the vehicle speeds at the compact roundabouts
were similar to larger modern roundabouts, at a fraction of the cost.
Jay Drye: "It would cost a million to $2 million at each
intersection to do something like that. And there was just no funding
available for that type of solution at the time.
These were about $100,000 per intersection, so a fraction of the overall cost."
Some didn't think the roundabouts would adequately accommodate
all vehicles, especially large trucks.
[truck noise]
Chris Damitio: "We recognized here that we needed to get the trucks through,
and we weren't going with as big a roundabout as traditional.
And so, with that in mind, and to save cost, we went with a flat center,
so that trucks could traverse more easily through the roundabout."
[traffic passing]
Dina Swires: "But we showed with the data that, trust us, the motorists
do react just like they have shown in the past.
And that was the biggest convincing factors for
the stakeholders in the Slater Road roundabouts."
The analysis enabled the team to customize the project
to the safety needs and budget of their location.
Jared Cassidy: "That way you don't build a project that's unnecessary
for what's happening at that location.
You can really hone in on what is the issue and focus
on that as a part of the safety piece of that project."
Dina Swires: "But it really takes thinking out-of-the-box,
using the tools that are available at hand,
tweaking designs, and seeing that sweet spot
where you're optimizing your existing location,
your existing roadway prism, but maximizing the safety."
The compact roundabouts alleviated the traffic problem, fit into the existing budget, and
provided a safer roadway for travelers.
Chris Damitio: "We don't see those backups on the interstate anymore,
down the ramp onto the interstate.
The county road behind me is functioning just wonderfully."
Dina Swires: "And now we have Level Service 'B' and the
safety benefits of a roundabout. We almost can't sleep
at night, now that we know we can put in roundabouts
for a hundred thousand in a weekend.
We almost can't not do something, because we have proof now."
♫ music ♫