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Accessibility and Mobility Differences

Accessibility

Access to retail and business opportunities in Ashland Accessibility (or just Access) is the ability to reach desired goods, services, activities and destinations (together called opportunities). A stepladder provides access to the top shelf in your kitchen. A store provides access to goods. A library, telephone and the internet provide access to various types of information. A highway or transit improvement can increase the services and jobs accessible from a neighborhood.

Access is the ultimate goal of most transportation, excepting the small portion of travel in which movement is an end in itself, (e.g., cruising, historic train rides, horseback riding, jogging). Even recreational travel usually has a destination, such as a resort or a campsite.

Four general factors affect physical accessibility:

  1. Mobility, that is, physical movement. Mobility can be provided by walking, cycling, public transit, ridesharing, taxi, automobiles, trucks and other modes.
  2. Mobility substitutes, such as telecommunications and delivery services. These can provide access to some types of goods and activities, particularly those involving information.
  3. Transportation system connectivity, which refers to the directness of links and the density of connections in path or road network.
  4. Land use, that is, the geographic distribution of activities and destinations. The dispersion of common destination increases the amount of mobility needed to access goods, services and activities, reducing accessibility. When real estate experts say “location, location, location” they mean “accessibility, accessibility, accessibility”.

Accessibility reflects the generalized costs (time, money, discomfort and risk) needed to reach activities. Where the marginal financial cost of travel is relatively low (for example, for automobile owners), travel time tends to be the dominant component of accessibility. Individuals often evaluate accessibility in terms of convenience, that is, the ease with which they can reach what they want. A shop that is relatively accessible to consumers is called a convenience store, and a home near common destinations is said to have a convenient location.

Given enough time and money nearly every location on earth is accessible, but the degree of accessibility varies widely, depending on the location, time and person. The relative degree of accessibility effects where you go, what you do, who you know, your household costs, and your opportunities for education, employment and recreation. Accessibility can affect the types of business, property values and economic development that occurs in an area.

Accessibility can be viewed from different perspectives, such as from the perspective of a particular location, a particular group, or a particular activity. It is therefore important to specify the perspective being considered when describing and evaluating accessibility. For example, a building with stairs and no elevator may be easily accessible for physically able people, but not for people with physical disabilities. A particular location may be very accessible by automobile but not by walking and transit, and so is difficult to reach for non-drivers. A building may have adequate automobile access but poor access for large trucks, and so is suitable for some types of commercial activity but not others.

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Mobility

An Amtrak train offers long-distance mobility Mobility refers to physical movement, including travel by walking, cycling, public transit, taxi, private automobile and other motorized modes. In general, increased mobility increases access. All else being equal, the more you can travel the more destinations you can reach. Mobility is evaluated based on travel distance and speed.

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Accessibility vs. Mobility

Transportation options enhance Portland's accessibility Cities and other major activity centers tend to have a relatively poor vehicle mobility (due to congestion), but are economically successful due to excellent accessibility (activities that are clustered together and many travel options). This indicates that in the game of economic competitiveness, accessibility trumps mobility.

This suggests that traffic congestion itself is not necessarily a major constraint on economic activity provided that land use patterns minimize the amount of driving needed to reach common activities and destinations, and that travelers have good transport options to choose from. Roadway level of service or average per-mile vehicle operating costs are less important indicators of transport system performance than average per-capita commute travel time and total per-capita transportation expenditures. Smart growth strategies that result in more accessible land use may be the best way to improve transport and increase economic productivity, because they reduce the average distance between destinations and therefore total travel costs, while a congestion reduction strategy may provide little or no economic benefit overall if it stimulates sprawl which reduces overall accessibility in a community.

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Other Meanings of "Access"

The word “access” has several specific meanings in transportation planning. In pedestrian planning it often refers to accessible design or universal design, meaning facilities designed to accommodate people with disabilities and other special needs. For example, a pathway designed to accommodate people in wheelchairs may be called “accessible.” In roadway engineering “access” refers to connections to adjacent properties. A “limited access” highway has minimal connections to adjacent properties, while a local road provides direct access. Access management refers to programs to limit the number of driveways and intersections on highways to improve traffic flow and safety.

Adapted from: Litman, Todd, Accessibility: Defining, Evaluating and Improving Accessibility, VTPI, 2005.

For an excellent paper discussing differing approaches to measuring transportation system performance, see Litman, Todd, “Measuring Transportation: Traffic, Mobility and Accessibility,” ITE Journal, Vol. 73, No. 10, October 2003, pp. 28-32.

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