Tuesday, December 28, 2010

Why we walk

One of CREC's primary goals is to create tools that help planners assess the pedestrian environment and identify what changes to make in order to allow residents to walk instead of drive.  Fortunately, this is a hot topic these days, and there are a growing number of websites that provide information about how well-suited a given location is for walking.  Taking a spin through a few of these websites is a good way to investigate in more depth what a "walkable" neighborhood means.

Probably the most well-known web-based walkability tool is Walk Score.  According to Walk Score, we walk if there are places nearby to walk to.  The site rates a location on a scale from 0 to 100 based on its proximity to amenities across several different categories, including stores, entertainment districts, banks, schools, and libraries.  Below is a screen shot showing Walk Score's assessment of the area around CREC's headquarters in Berkeley:

Researchers often talk about the "four Ds" of land use--density, diversity of uses, pedestrian design, and access to destinations--that studies have shown to reduce driving, and implicitly, to increase walking.  Of the four Ds, Walk Score addresses access to destinations most directly, but also density and diversity of uses, since presumably more compact and mixed use neighborhoods will have shorter distances between homes and the amenities that Walk Score examines.  Of course, whether you actually visit the destinations that Walk Score looks at is another question--as a lunch spot, Adagia is out of our price range, and Urban Outfitters doesn't quite offer the professorial tweeds favored by researchers--but I generally find it to be a pretty accurate tool regardless, because of the way that amenities cluster together in commercial districts.

Another tool that Walk Score has recently unveiled focuses more narrowly on accessibility.  Its Transit Time Map shows you all the places that you can reach within 45 minutes of a given point by walking and taking transit.  According to this tool, you're more likely to walk if you can get farther without a car.  Since CREC headquarters is a pretty long walk from the Downtown Berkeley BART station, we can only make it a few BART stops in either direction, even if we head out during the evening rush hour, when trains are running most frequently:

Mapnificent is another tool that measures accessibility.  Unlike the Transit Time Map, Mapnificent uses average transit headways and travel times, rather than adjusting your range depending on when you take your journey.  But it makes up for this lack of precision by allowing you to adjust your travel time and other factors, including whether or not you have a bicycle, as well as including some nice rainbow color-coding.  Mapnificent confirms a hypothesis that I've come up with in the course of my commute, which is that I need a bike in order to get from my neighborhood in San Francisco to CREC's offices in under an hour.  Here's my 55-minute travel radius with a bike:

And here's the same radius without a bike:
The one D that these tools leave out is pedestrian design.  As far as the Mapnificent and Walk Score are concerned, it doesn't matter whether there's a wide pedestrian-only path or an interstate highway connecting you and the nearest coffee shop (fortunately in our case it's the former, which helps to prevent accidents on drowsy Monday mornings).  The Walk Score team readily acknowledges this shortcoming, and is working to overcome it, but critics of the tool claim that the lack of consideration for design is a fatal flaw--see the Conservative Planner's post on the topic for a number of examples where Walk Score gives high rankings to neighborhoods in which walking would be tantamount to suicide.  However, the designers of tools like Walk Score and Mapnificent are doing the best they can with the data that is readily available, and currently there's no database of sidewalk conditions or other pedestrian amenities out there--nor is there even a standardized way for cities to collect this data.  This is something that we're working to develop here at CREC.

In the meantime, Walk Score has caught on with real estate agents, who frequently use it to promote properties in pedestrian-friendly neighborhoods, and both the designers of the Transit Time Map and Mapnificent express hopes that their tools can help people locate neighborhoods in which they can live a car-free lifestyle.  More importantly, these tools continue to foster a lot of discussion about the benefits of compact, walkable neighborhoods, which is an important first step in reversing several decades of car-oriented planning.

Wednesday, December 1, 2010

Reaching 2050 Climate Goals II: The Critical Role of VMT

In my previous post, I described the magnitude of the challenge facing California (and all of industrialized society) in meeting the greenhouse gas emissions goals that science and state policy agree are necessary.

A key conclusion of this discussion is the fact that all sectors of the economy must achieve deep reductions, not just one or two. This certainly includes the transportation system, which in California is the largest single source of GHGs (38 percent of the total, according to the California Air Resources Board). Transportation-related emissions, in turn, are a product of three factors:
  • The fuel efficiency of vehicles
  • The carbon content of fuels
  • Vehicle miles traveled (VMT)
Multiplying those three factors yields the total carbon emissions. Therefore, unless the fuel stock for vehicles can be totally decarbonized within 40 years (e.g. perhaps by conversion to an electric vehicles fleet powered entirely by carbon-free renewable energy), there will once again have to be substantial improvements in all three areas in order to bring the transportation sector as a whole into line with an 88 percent per capita emissions reduction relative to today's levels (see previous post for an explanation of how that number is derived).

What does this really mean in practice? Well, if we think of fuel efficiency and carbon content collectively as "carbon efficiency" (or carbon emission per mile), then we see that the carbon efficiency times the VMT must be reduced on the order of 88 percent per capita in forty years. If carbon efficiency were quintupled over that time period through a combination of fuel efficiency gains and decarbonization of fuel stocks, we would still need to reduce VMT by 40 percent per capita relative to today's levels. In other words, we would have to "make do" with 40 percent less personal driving, trucking, business travel and all other uses of motorized vehicles. If carbon efficiency is merely doubled, we would need to reduce the per capita VMT by 76 percent!

Are these changes feasible? Certainly. In fact, there are Americans right now who live well on 76 percent less VMT than their average compatriots. They're the Americans who live in dense urban centers such as New York and San Francisco. Bringing the transportation system into line with our 2050 climate goals means making sure (among other things) that vastly more Americans can live in those kinds of truly dense, mixed-use environments, rather than simply somewhat-more-dense suburban settings (which tend to achieve VMT reductions of only about 20-30 percent).

It can be done -- but modest changes to how we build urban regions won't get us there.