Saturday, August 30, 2014

How much vehicle traffic should a main street have?

Westmoreland district, Portland. Image: Ashley Brandt

Picture a vibrant neighborhood business district in an American city – one that’s located outside of the downtown area. Or, envision the main street of one of your favorite small towns. Think cafes, restaurants with sidewalk seating, quirky stores, street trees, two- to four-story buildings close to the sidewalk, people strolling about.

Now, what is the car traffic like? Is it busy? Too busy? Not busy enough? Moving too fast? Not moving at all? Or is it just right?

Some might ask, isn’t the number of people walking along a main street more important than the traffic volume? In theory, yes, but not all of these people walked here directly from their houses. Some may have taken public transit or ridden their bikes. Many people probably drove and parked – either on their way to somewhere else, or specifically to visit this part of town.

The reality is, unlike in much of the rest of the world, American main streets need car traffic to thrive. If traffic volumes are too low, businesses don’t get the visibility they need to attract customers. American experiments in pedestrian-only main streets have been largely unsuccessful, with a few notable exceptions such as Church Street in Burlington, VT or Washington Street in Cape May, NJ.

Conversely, if traffic volumes are too high, the main street doesn’t feel safe and pleasant enough for people to stroll or eat an ice cream cone on the sidewalk. Major arterials with four or more lanes of heavy traffic have proven difficult to foster a pedestrian-friendly business environment. Instead, they often attract gas stations and discount stores. Only a few urban boulevards have bucked this trend – usually with major beautification and traffic calming investments.

Portland's Mississippi Avenue. Image: Scott Keith
Is there a “Goldilocks” traffic volume for main streets in neighborhood business districts and small towns? I would argue that there is, and that it’s within a range of 5,000 to 15,000 vehicles per day. My evidence, far from exhaustive, is based on traffic counts from 26 neighborhood business district main streets in Portland, Oregon. With few exceptions, Portland’s most vibrant, successful neighborhood main streets – Mississippi, Alberta, NW 23rd, for example – have 5,000 to 15,000 cars drive through on an average day.

There are successful outliers, from Clinton Street’s modest 2,300 motorized vehicles (which join more than 3,000 daily cyclists on this busy bike boulevard), to the 18,000 vehicles seen daily on both Hawthorne and East Burnside (both 4-lane roads). But most good main streets are in the Goldilocks range. Three of them – Milwaukie Avenue in Westmoreland, inner Division Street and Belmont Street – have daily volumes around 12,000.

Once you surpass 20,000 vehicles per day, conditions for a traditional main street deteriorate, as seen on 82nd Avenue and Barbur Boulevard. Surpass 40,000 – as on McLoughlin Boulevard – and it’s very unlikely you will be able to create a pedestrian-oriented main street at all.

Of course other factors play into the success of a main street, particularly the economic characteristics of the surrounding neighborhood and urban design features like setbacks, massing, trees and transparency.  Even within the transportation realm there are other factors to consider, such as parking availability, number of traffic lanes, sidewalk width and spacing of pedestrian crossings. But vehicle volumes are nevertheless an important indicator.

The table below reports average daily traffic volumes for 26 neighborhood business district main streets in Portland, listed in ascending order of average daily traffic. Those familiar with Portland will notice how the viability of these main streets drops off toward the bottom of the list.

Sources: Portland Bureau of Transportation and Oregon
Department of Transportation
Looking at these figures, it’s worth pondering where we should plan for future main streets. Portland Metro regional policy calls for vibrant mixed use “corridors” along arterial roadways with transit service. But will that work everywhere? I’m not convinced that busy suburban highways like 185th Avenue in Washington County, McLoughlin Boulevard in Clackamas County, or outer Division Street in Portland will ever become thriving, pedestrian-oriented main streets.

I think there’s more potential along intersecting roads that have lesser volumes and fewer lanes, like Alexander Street in Aloha or Oak Grove’s namesake boulevard in Clackamas County. These collector streets are visible from the busier arterials, but offer a quieter, safer and more intimate setting for pedestrian-friendly businesses. One of Oregon’s best examples of this is 3rd Street in McMinnville, a cozy two-lane main street perpendicular to bustling Highway 99W.

I believe we should question the expectation that our busy, multi-lane arterial roads can also be excellent main streets. Perhaps we should focus our commercial revitalization efforts on the Goldilocks streets – the ones with 5,000 to 15,000 vehicles per day.

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