In December 2008 the City of Portland and Alta Planning released an analysis they called a “Cycle Zone Analysis” (top two maps above). Although somewhat qualitative it identify the strengths and weaknesses of bicycling in different zone of the city. Myself and many other professions were very excited about this because it helped to fill a gap in non-motorized transportation planning and analysis.
Most non-motorized transportation planning is based on citizen input through needs analysis. Essentially someone will say “there is a need here”, like lack of sidewalk, or lots of bicyclist use this road, etc. This is an extremely important part of transportation planning, after all if you don’t know what is wrong how can you solve it. But stopping there, as many plans do, leaves you with distinct problems. First you aren’t able to easily compare how important a project is. This is especially important when identified projects far outstrips funds, sound familiar? Also this make it hard to quantify or understand from a long range planning perspective what your strengths and weaknesses are, and in turn how to best build off your strengths and mitigate your weaknesses.
More after the jump…
This is why the Cycle Zone Analysis was so important. The major drawback however was that it had a low “resolution”, with some zones as large as several square miles. This has been solved using raster-based GIS Multi-Criteria Evaluations (MCE). The Seattle Pedestrian Master Plan relied heavily on this type of analysis as well as the Bike-Share Feasibility Report which I reported on yesterday.
So two months ago when I started taking an advanced GIS class I decided to do a Seattle bicycle analysis as my final project. I started the project by recreating the Cycle Zone Analysis of Portland, and then using the same factors and weights to do an analysis of Seattle. The maps above are a comparison of the original Cycle Zone Analysis and my analysis. While the results certainly are not fact and are the results of multiple subjective factors and weights, I think they are accurate enough to draw some conclusions from while also raising some interesting questions. The analysis takes street connectivity, land use, bicycle facilities, slope and barriers into account. These factors were then weighted and the resulting maps are a combination of these factors and applied weights. Please see the report for more detail.
The analysis shows that while Portland is already very bikeable, Seattle has a long way to go. Portland’s most bikeable areas are in the city center and inner city neighborhoods. Neighborhoods outside the city center are still fairly bikeable, especially in the higher density areas or in areas with decent bicycle facilities. In contrast Downtown Seattle is not very bikeable, with surrounding center city neighborhoods doing a bit better. The very low score in Downtown Seattle is probably too low due to an problem with the analysis (see Section 7.2.1 of report). The most bikeable areas of Seattle are those located near multi-use paths like the Burke and Elliot Bay trails with central Fremont having the highest score. As someone who lived around the corner from the Troll for 6-months I can attest to the great bikeability of the area.
This second pair of maps only takes permanent things like slope, street connectivity and land use into account. By only using these factors the potential of the area can be analyzed. The maps essentially shows where the factors come together (dense, flat, grid street network) or don’t come together (not dense, hilly, winding streets). What you will notice is that while both downtowns have very high or high scores, Portland has fairly uniform and good bikeability across the city while Seattle is spotty with “islands” of high or good bikeability surrounded by areas of low bikeability. Its interesting to note that many of Seattle’s Urban Villages are in the center of these bikeable islands. While this is partially due to land use it also reflects the fact that many Urban Villages are located either on the top of a hill or in the bottom of a valley. Ballard looks more like a Portland neighborhood than a Seattle neighborhood.
To me one of the largest takeaways of this analysis is that both cities should pursue different bicycle facility investment strategies. While Portland should try to blanket the city with a grid-like bicycle network, Seattle needs to be a bit more intentional. Building off the concept of islands, Seattle should focus on connecting the most bikeable areas with high quality facilities. A second objective should focus on improving circulation within these islands. These two objectives build of off the inherent strengths of the city. However unlike most of Portland, Seattle has significant weaknesses due to topography. To overcome these obstacles higher speed and higher quality transit service that is well integrated with the bicycle network is extremely important. In this ways transit compensates from the lower potential of biking between these islands.
I think that Beacon Hill is a perfect example. While biking from Beacon Hill to anywhere else in the city is a fairly hilly proposition, biking on Beacon Hill is fairly reasonable and easy. So while higher speed and higher quality transit (LINK) are best for “multi-island” trips, bikes and bicycle facilities are better at connecting residents to neighborhood businesses and transit.