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Access Scores – Measuring the Why, Where and How of Accessibility

Chris McCahill, Senior Associate – Smart State Transportation Initiative
Matt Pettit, Product Engineer – Citilabs
Chris Sinclair, President – Renaissance Planning Group

 

Planners are tasked with more than just designing, evaluating and planning transportation mediums - they are often asked to help us feel more comfortable with moving around our communities and feel a greater sense of “livability.”  But how do we quantify “liveability?”   What makes a place feel more “liveable?”

How we personally evaluate our community is in how it supports our daily life. Think about it - how often do you ask yourself something like:

  • Do I want to drive that far for my job?
  • Wouldn’t it be nice to walk the kids to school?
  • Can I walk or bike to restaurants and grocery shopping?
  • Do people get out of their houses and walk around in this neighborhood?

And we ask ourselves these questions because the ease of completing these tasks, how accessible we are to the things that impact our daily life is how we evaluate the livability of our communities.

So how do planners approach the seemingly gargantuan task of creating greater livability? Too often the focus is on simply moving vehicles quickly when we should really be asking ourselves: Why are the vehicles there to begin with? Where are they going? How do we get people to what they need more efficiently?

Accessibility - The Why, Where and How Bridge

Accessibility to destinations we care about has long been an important topic in city planning, but it has just recently become easier to quantify. Accessibility measurement simultaneously considers the why, where and the how of connecting, and provides the ability for land use and transportation planners to know what to change in order to optimize connectivity. If people have easy access to local destinations, they don’t have to travel greater distances, will more likely spend their money locally, and could even choose to walk. In this way, accessibility affects the number of vehicles on the road, time spent traveling, travel distances, the ability to travel by different modes, and even the quality and economic productivity of a place.

That is why the Brookings Institute announced recently that they are launching their own “Moving to Access” initiative as part of their Metropolitan Policy and Global Economy and Development Programs. The initiative “aims to inform and promote a more socially focused ‘access-first’ approach to urban transportation policy, planning, investment, and services,” according to a press release from the institute. In a recent presentation by Brookings Fellow, Adie Tomer, measurement of accessibility was cited as one of the major issues in the way of moving forward with accessibility over mobility.

In an effort to standardize measurement of accessibility, Citilabs, Renaissance Planning Group and The State Smart Transportation Initiative (SSTI) have partnered to formulate two overarching accessibility measures. These measures score accessibility in terms of the transportation needs of individuals throughout the day, and have the ability to describe how individuals travel (mode) and how much they will travel (vehicle miles traveled or VMT). These two measures are:

  • Access Score – Work
  • Access Score – NonWork

 

Access Score - Work describes an individual’s ability to reach employment opportunities.  These could be jobs of all types, or specific jobs based on industry or wages.  The score describes people’s ability to make what is often their two most important trips of the day when demand is usually highest and greatly influences what mode of transportation they choose throughout the rest of their day.

 

Access Score – NonWork describes an individual’s ability to reach non-work destinations, often as part of their daily routine.  These destinations include grocery stores, schools, restaurants, parks, pharmacies and other common destinations.  Overall, non-work trips make up almost 85% of all household travel and more than 70% of household vehicle miles traveled (VMT) in the U.S.1 The ability to make these household trips are expressed through Access Score – NonWork and focuses on the potential transportation mode that may be chosen to make those trips.

In examining the foundation of these measures, there are aspects of an individual’s trip that determines the look and feel of that trip.  Also known as the utility of one’s trip, it is more than just the underlying travel time of the trip.  Rather, aspects that might determine the likelihood a person is going to make that trip, how they make the trip (mode), and when they may make the trip.  These could include:

  • What types of destinations are close to the individual?
  • What’s the relative convenience of each mode of travel for an individual to their destination?
  • How close are the destinations to the individual?
  • How does the time at which the individual travels affect their trip?
  • What’s the experience of an individual en route to their destination?

Let’s examine each of these questions…

Location and Diversity of Destination Types
An individual’s daily trips are based not only one type of destination but rather a variation of destinations.  Access Score – NonWork values the number and type of each destination (Grocery Stores, Restaurants, Schools, Parks, Medical Centers, etc…) within relative close proximity to the individual.  Access Score – Work focuses on different job opportunities throughout the region, these may be centrally located, or sparsely populated throughout the suburbs.

Transportation Mode
People’s choice of walking, biking, public transit, or driving depend on the location of their destination and the relative cost and quality of the different travel options. The accessibility measures are determined for each mode of transportation, allowing for a better understanding the trade-offs and individual mode choices.

Individual’s Value of Time
As an individual, destinations that are close and require shorter travel times offer greater utility.  Job seekers, for example, may place a high value on opportunities within a very short distance from their home, but also value the choice of many opportunities somewhat farther away.  Both Access Scores account for the utility of each trip that an individual may make, valuing a destination that is 10 minutes away more than a destination that is 30 minutes away.

Time of Day Differences
Individuals make different type of trips at different times of the day.  From someone working a typical 9 – 5 job to another working a midnight shift, an accessibility measure must capture the unique aspects of each of their commutes.  These aspects include traffic congestion or public transit service availability throughout the day.  The Opportunities and Lifestyle Access Scores take into account the change in accessibility throughout the day, or week, to reflect the needs of different people for different types of trips.

Travel Experience
Often, accessibility is measured solely in terms of travel time.  Individual travel decisions, however, are not based solely on travel times but also on the quality, comfort, and safety of their travel experience.  This pertains both to the transportation mode and the route they choose.  For walking trips, an individual may prefer roads with less traffic, lower speeds, and a sidewalk, which in turn affects the destinations they have access to.  The accessibility measures account for different roadway conditions such as the speed limit, number of lanes, intersection configuration and roadway type (arterial vs. neighborhood).

Industry Standard

The performance measures of Access Score – Work and NonWork have the potential to explain important outcomes such as transportation mode choices, total travel, community health, and economic productivity. In fact, the Commonwealth of Virginia has already begun using the scores as one of their six measures for prioritizing projects in their Smart Scale initiative, which scores projects on their merits rather than political wrangling.

Virginia is just the beginning. As we heard in several conversations at the recent TRB Annual Meeting in Washington, DC, more state DOTs are looking to the SMART SCALE program as the template to follow. And as Transportation Performance Measures gain more adoption, a standard will certainly emerge. Access Score - Work and Nonwork will help establish a foundation moving transportation planning forward and reach the widespread sustainability goals being put forth in the industry.

1 http://nhts.ornl.gov/2009/pub/stt.pdf

 

Online Webinar:

Please join Chris McCahill of SSTI and Matt Pettit of Citilabs on Thursday, March 30 at 2:00PM to learn more about these new standard accessibility measures.

Watch Now


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