Online TDM Encyclopedia - Accessibility

Evaluating People’s To Reach Desired Goods, Services And Activities

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Victoria Transport Policy Institute

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Updated 4 January 2009

This chapter defines the concept of “accessibility,” discusses how it is evaluated, and describes various ways to improve it. Accessibility refers to the ability to reach desired goods, services and activities, which is the ultimate goal of most transportation activity. For more detailed discussion see the report “Accessibility: Defining, Evaluating and Improving Accessibility .”

Description

Accessibility (also called access or convenience) refers to the ability to reach desired goods, services, activities and destinations (together called opportunities). For example, a stepladder provides access to a high shelf, a store provides access to goods, and a library or telecommunications device provide access to information. Walking, cycling, ridesharing and public transit provide access to jobs, services and other activities. 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 (mobility as an end in itself is discussed later in this chapter).

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.

Table 1 lists specific factors that affect accessibility and the degree to which they are considered in current transport planning. Some of these factors tend to be overlooked or undervalued, such as nonmotorized travel demand, alternative mode service quality, land use factors, traffic impacts on nonmotorized access, and mobility management options.

Table 1 Summary of Factors Affecting Accessibility (Litman, 2007)

Name	Description	Current Consideration
Transport Demand	The amount of mobility and access that people and businesses would choose under various conditions (times, prices, levels of service, etc).	Motorized travel demand is well studied, but nonmotorized demand is not. Travel demand is often treated as inflexible rather than variable.
Basic Access and Mobility	The relatively high importance to society of some mobility and accessibility activity.	Considered in some types of planning, such as special mobility services.
Mobility	The distance and speed of travel, including personal mobility (measured as person-miles) and vehicle mobility (measured as vehicle-miles).	Conventional transport planning focuses primarily on mobility, particularly vehicle mobility.
Transportation Options	The quantity and quality of access options, including walking, cycling, ridesharing, transit, taxi, delivery services, and telecommunications. Qualitative factors include their availability, speed, frequency, convenience, comfort, safety, price and prestige.	Motor vehicle options and quality are usually considered, using indicators such as roadway Level-of-Service, but other modes lack such indicators and some important service quality factors are often overlooked.
User information	The quality (convenience and reliability) of Multi-Modal Navigation Information.	Frequently considered when dealing with a particular mode or transport problem, but often not comprehensive.
Integration	The degree of integration among transport system links and modes, including terminals and parking facilities.	Automobile transport is generally well integrated, but connections between other modes are often poorly planned.
Affordability	The cost to users of transport and location options relative to incomes.	Automobile operating costs and transit fares usually considered.
Mobility Substitutes	The quality of telecommunications and delivery services that substitute for physical travel.	Not usually considered in transport planning.
Land Use Factors	Degree that factors such as land use density and mix affect accessibility.	Considered in land use planning but given less consideration in transport planning.
Transport Network Connectivity	The density of connections between roads and paths, and therefore the directness by which people can travel between destinations.	Current planning supports hierarchical road networks, but there is growing support for more connected systems.
Roadway Design and Management	How road design and management practices affect vehicle traffic, mobility and accessibility.	Some factors are generally considered, but others are not.
Mobility Management	Various strategies that increase transport system efficiency.	Often overlooked or undervalued by mobility-based planning.
Inaccessibility	The value of inaccessibility and external costs of increased mobility.	Not generally considered in transport planning.

This table indicates factors that affect accessibility and whether they are currently considered in planning.

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, in 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.

Think about the destinations you can reach within 10 minutes, 30 minutes and 60 minutes of your home or worksite. Most people expect to spend less than 10 minutes of time and less than a dollar in financial costs on travel for common errands such as snacks, and minor shopping. If goods and services are available within a convenient ten-minute walk of your home or worksite, you may perform some errands by walking, but if not you will probably drive. Thirty minutes and two or three dollars represent the time and money most people expect to devote to a one-way commute. Sixty minutes and a few dollars represent what people will typically travel for a special event. A sports stadium, concert hall or airport will primarily attract patrons who are accessible within this range. (Of course, maximum travel costs vary depending on personal preferences and conditions, but these are reasonable averages).

Other Meanings of “Access”

The words “accessibility” and “access” have many meanings and implications. This chapter focuses primarily on physical access to goods, services and destinations. There are other factors that affect access. For example, access to medical services requires not only physical access to medical facilities, is also that services be affordable and understandable to potential users.

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.

Evaluating Accessibility

Transportation Evaluation refers to various methods to predict determine how a particular decision or activity affects accessibility, and the value to society that results. For example, public officials may want to compare how particular highway improvements, transit improvements, TDM programs and land use changes would affect access by residents to public and commercial services.

How transportation is Measured can affect how accessibility is evaluated, and the range of solutions that are considered to transportation problems. Standard transport Modeling and Evaluation techniques tend to be traffic-based, that is, they can predict how transport and land use changes affect motor vehicle movement, and so favor automobile-oriented transport improvements. In recent years, mobility-based evaluation techniques, which measure the movement of people and goods, have become more common. This tends to give greater consideration to transit and ridesharing, but still treats movement as an end in itself. Measuring transport in terms of access expands the range of impacts and solutions further to include mobility substitutes and land use factors. Table 2 compares these different ways of measuring transportation.

Table 2 Comparing Methods of Measuring Transportation

	Traffic	Mobility	Access
Definition of Transportation	Vehicle travel.	Person and goods movement.	Ability to obtain goods, services and activities.
Unit of measure	Vehicle miles.	Person-miles and ton-miles.	Trips, generalized costs.
Modes considered	Automobile and truck.	Automobile, truck and transit.	Automobile, truck, transit, cycling and walking.
Common Indicators	Vehicle traffic volumes and speeds, roadway Level of Service, costs per vehicle-mile, parking convenience.	Person travel volumes and speeds, road and transit Level of Service, cost per person-mile, travel convenience.	Quality of available transportation choices. Distribution of destinations. Cost per trip.
Assumptions concerning what benefits consumers.	Maximum motor vehicle travel and speed.	Maximum personal travel and goods movement.	Maximum transport choice and cost efficiency.
Consideration of land use.	Treats land use as an input, unaffected by transportation decisions.	Recognizes that land use can affect travel choice.	Recognizes that land use has major impacts on transportation.
Favored Transportation Improvement Strategies	Roadway and parking facility improvements to increase capacity, speed and safety.	Transportation system improvements that increase capacity, speeds and safety.	Management strategies and improvements that increase transport system efficiency and safety.
Implications for TDM	Generally considers vehicle travel reductions undesirable, except if congestion is extreme.	Supports TDM strategies that improve personal and freight mobility.	Supports TDM whenever it is cost effective.

This table compares three common perspectives used to measure transportation.

Accessibility is a well-recognized concept in the disciplines of geography and urban economics, and transportation professionals have begun to explore its implications for transport planning (BTS, 1997). Accessibility is more difficult to measure than mobility because it is affected by a variety of factors, including mobility by various modes, mobility substitutes and land use conditions (Neimeier, 1997; Zhang, 2005). Some accessibility models have been developed, but they tend to be expensive to build and are generally applied on a regional scale (Kockelman, 1996; Abraham, 1998; Dong, et al, 2006).

Accessibility Versus Mobility

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 are clustered together and there are 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 (Measuring Transport). 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.

Other Accessibility Indicators

Some other methods for evaluating accessibility are described below. For additional information see the Transportation Options chapter.

Specific Accessibility Problems

There is often a specific accessibility problem or constraint, such as the need for a particular group of people to access medical services. Improvements can be evaluated based on their ability to address this problem or overcome a particular constraint. For example, policy makers may compare strategies that locate medical services closer to users (e.g., more community-based medical clinics), locate more residents closer to medical services (e.g., encourage the development of senior housing in areas with good medical services), increased mobility for medical care users (e.g., special shuttle and ridematching services to medical centers), and addressing mobility barriers (e.g., insuring that all public transit buses can accommodate wheelchair users).

User Perspective

Another approach for evaluating accessibility is to consider how well a particular individual or group’s access needs are met, the barriers they face, and how their accessibility could be improved. For example, it may be important to consider how well elderly non-drivers are able to access medical, commercial, social and recreation access needs. Resort community planners may want to consider how well various types of visitors (e.g., families with young children who do not have a car, people with physical disabilities, teenagers) are able to access activities and amenities.

Strategic Planning For Transportation Options

This approach involves evaluating policies and projects according to whether they tend to increase or reduce accessibility. For example, zoning codes, parking requirements, new developments, roadway design, and transportation agency expenditures can all be evaluated in terms of whether they tend to increase or reduce overall accessibility, that is, their impacts on the range of transportation options available and the distribution of locations in an area. This approach focuses on whether accessibility objectives and indicators are properly incorporated into the planning process.

Equity Analysis

Accessibility has important Equity impacts. The quality of a person or group’s access determines their opportunity to engage in economic and social activities. Policies that favor access for one group over others can be considered unfair (horizontally inequitable). Policies that favor advantaged groups over disadvantaged groups (such as wealthy over poor or motorists over non-motorists) can be considered vertically inequitable.

Equity analysis of accessibility often focuses on providing Basic Access to people who are physically, economically or socially disadvantaged. In most communities, people who can drive and afford a vehicle have relatively little trouble accessing medical services, stores, education, employment or social/recreational activities (although access under urban-peak conditions may be slow due to congestion). However, there are often many people who cannot achieve Basic Access due to physical, economic or social barriers.

Basic Access and transportation disadvantage reflect qualitative factors that may be difficult to measure, and values that may vary from one individual or community to another. For example, different people may have different ideas as to how far physically-able transit users should be expected walk to access a bus, or how many shopping and recreation trips should be provided by special transit services to people with disabilities. For this reason it is important to involve community members and users in determining how to evaluate accessibility equity.

Travel Impacts

Improved accessibility can have a variety of travel impacts. For example, if employees are allowed to telecommute, some may reduce their total vehicle travel, while others will use it as an opportunity to live farther from their worksite. Improved walking and cycling conditions may lead to more recreational walking, not necessarily a reduction in driving. Similarly, improved accessibility to shops may result in more shopping trips, with no change in the total amount of shopping travel.

People throughout the world tend to spend about the same amount of time on travel, averaging about 1.2 hours per day (Schafer, 2000). After all, there are only so many hours in a day, part of which is devoted to sleep, work and other personal activities. As a result, people tend to adapt their lives to their accessibility. For example, when a person first obtains a bicycle or automobile, they don’t usually simply travel faster to the same destinations, they usually spend about the same amount of time traveling to more distant destinations. Conversely, if your accessibility improves, for example, if several stores open near your home, you may visit them more frequently than if shopping trips require several miles of travel. As a result, travel time budgets tend to remain constant as mobility and land use accessibility change.

Improved accessibility provide consumer benefits, and it can help achieve TDM objectives such as reduced congestion, pollution or crashes, particularly if matched with incentives to reduce automobile travel. For example, improvements in transportation options and land use accessibility can offset the negative consumer impacts of strategies such as Parking Pricing, Road Pricing and Vehicle Restrictions. The TDM Evaluation chapter describes how to account for the various travel and economic impacts of changes in accessibility.

Strategies to Improve Access

There are many ways to improve accessibility. Major categories are described below.

Table 3 Potential Accessibility Improvement Strategies (VTPI, 2006)

Factors	Improvement Strategies
Access and Mobility Demand	Use research to better understand people’s accessibility and mobility needs, preferences and abilities, and use social marketing strategies to develop better options that respond to these demand, and to encourage consumers to choose more efficient and equitable options.
Basic Access and Mobility	Prioritize transportation improvements and activities to favor access to goods, services and activities considered most important to society.
Mobility	Improve traffic speed and capacity, such as improving and expanding roadways.
Transportation Options	Improve the convenience, comfort, safety, reliability, affordability and speed of transport options, including walking, cycling, automobile, rideshare, taxi, carshare and public transit.
User Information	Improve the quantity and quality of User Information regarding travel and location options, including signs, maps, brochures, websites and telephone services. Special attention can be given to providing convenient information on alternative modes and efficient locations.
Integration	Improve connections between different modes and destinations, such as more integrated information, fares, walkability, baggage transfers, automobile and bicycle parking.
Affordability	Improve the quantity and quality of affordable modes (walking, cycling, ridesharing, public transit, taxi and telework), and improve housing affordability in accessible locations.
Mobility Substitutes	Improve the quantity and quality of telecommunications and delivery services that substitute for physical travel.
Land Use Factors	Improve land use accessibility by increasing density and mix, in order to create activity centers and urban villages that contain the appropriate combination of housing, jobs and services within convenient walking and cycling distance.
Transport Network Connectivity	Improve road and path connectivity to allow more direct travel between destinations, including special shortcuts for non-motorized travel where appropriate.
Roadway Design and Management	Improve roadways to increase traffic flow (for example, by reducing the number of driveways), to favor higher occupant vehicles, and to improve walking and cycling conditions.
Mobility Management	Use mobility and parking management strategies to improve travel options, to encourage users to choose more efficient modes, to favor higher occupant vehicles, and to encourage more accessible land use development.
Improve Payment Systems	Better road and parking pricing methods reduce transaction costs and increase the feasibility of implementing pricing reforms to increase overall transportation system efficiency.
Inaccessibility	Where appropriate, limit mobility and accessibility.

This table indicates various ways to improve accessibility. Current transport planning practices tend to focus on just a few of these strategies, which limits the scope of solutions considered.

Vehicle Travel

Transportation System: Building and paving more roads, increasing roadway capacity and design speeds, improving traffic flow management, improving parking facility capacity and convenience, reducing roadway risks, improving vehicle performance and safety, and minimizing vehicle user charges. However, in urban areas it is often not feasible to build enough road capacity to handle demand, leading to traffic congestion. Increasing roadway capacity may do little to reduce urban-peak travel demand due to latent demand (Rebound Effects).

Land use Patterns: Automobile accessibility improves if common destinations are located with convenient access to major highways and abundant parking capacity.

Ridesharing and Carsharing

Transportation System: Ridesharing can be supported with carpool matching services, vanpool programs, HOV Priority, Guaranteed Ride Home programs, and rewards for commuters who use this mode (Commuter Financial Incentives). Carsharing can be supported by insuring that such services are available in a community. Otherwise, strategies that improve automobile travel also support Ridesharing and Carsharing.

Land use Patterns: Ridesharing becomes more feasible if common destinations are Clustered together, with good pedestrian access between worksites and amenities such as restaurants and shops. Other land use factors that improve automobile transportation tend to improve these modes.

Transit Services

Transportation System: Transit Improvements include increased service, reduced fares, more convenient pricing systems, improved vehicles, HOV Priority, improved transit stations and waiting areas, improved rider information and Marketing programs, improved access to transit stops, Park & Ride facilities, improved Security for transit users and pedestrians.

Land use Patterns: Transit is most convenient if common destinations are closely clustered near transit stations and along corridors with maximum transit service, with pedestrian-oriented development within one-half mile of transit stops. Policies that encourage clustering, infill development, mixed land use, more attractive street environments, pedestrian and bicycle access and reduced automobile parking (except at Park & Ride facilities) improve transit accessibility.

Nonmotorized Transportation

Transportation System: Nonmotorized Improvements include improved sidewalks, crosswalks, paths, bikelanes, shortcut paths, Traffic Calming and Vehicle Restrictions, Safety education, law enforcement and encouragement programs, integration with transit (Bike/Transit Integration and Transit Oriented Development), Bicycle Parking and Address Security Concerns.

Land use Patterns: Higher-density, clustered, mixed land use is particularly important for pedestrian access. Narrow roads, short blocks and shortcuts that allow more direct access for nonmotorized travel. New Urbanist design features tend to support nonmotorized accessibility.

Mobility Substitutes

Transportation System: Improved telecommunications services, and Commute Trip Reduction programs that support Telework. Delivery services can be improved with policies that favor delivery vehicles over general traffic (e.g., allowing freight vehicles to use HOV lanes and delivery vehicle parking spaces).

Land use Patterns: Telework can function with virtually any land use pattern. Delivery services are more efficient with clustered development.

Land Use

Increased land use accessibility tends to reduce automobile trips and trip distances (Land Use Impacts on Transportation). A residence or worksite in an accessible location tends to generate significantly fewer automobile trips (typically 25% less), and the trips that occur tend to be shorter, than if the same facility is located in a more isolated location. Land use policies that increase the number of stores, schools, restaurants, jobs and friends within a community can have the same effect on accessibility as a technology that increases travel speeds. Programs that make accessible locations (such as older urban neighborhoods) more affordable, safer and socially acceptable can also improve access.

Best Practices

· Transportation should be evaluated based on Accessibility, rather than treating mobility as an end in itself.

· Transportation and land use planning should be integrated to optimize access. For example, land use policies should encourage clustering in areas that have good walking and cycling conditions, and good transit service.

· Transportation Planning should consider a wide range of strategies for improving Accessibility, including improvements to vehicle traffic, transit, nonmotorized transportation, mobility substitutes and more accessible land use.

· Accessibility planning should also consider efforts to improve consumer information, affordability, convenience, security and public image of transportation and land use options. Stakeholders should be consulted to identify all potential barriers they perceive to improved access.

· In higher density areas, the amount of land devoted to roads and parking should be minimized, for example, through Shared Parking and other Parking Management strategies.

· Special consideration should be given to providing Basic Access for people who are transportation disadvantaged, including Universal Design.

· Special consideration should be given to Pedestrian Improvements because pedestrian access is important on its own and critical for other modes and other TDM strategies, including ridesharing, public transit and parking management.

· Accessibility improvements should be implemented with incentives to reduce low-value automobile travel and encourage shifts to alternative modes.

· Analysis of strategies for improving access should consider impacts on different groups, locations and times. For example, a planner may say that “Widening this road will improve access for motorists, but reduces access for pedestrians and most transit users,” or “Increasing minimum parking requirements in the zoning code will improve automobile access, but may help create more dispersed land use patterns that are less accessible overall.”

· Transportation planning should account for the benefits of inaccessibility and the external costs of vehicle traffic. Transportation policies should limit access and mobility when doing so preserves valuable social or environmental amenities.

Wit and Humor

A city-slicker driving along a quiet country road stops to ask an old farmer for directions to a town in the next county.

The farmer ponders the question for a moment and replies, “I’m afraid you can’t get there from here.”

Note: This old joke is amusing because it contradicts what we know of transportation. Given accurate directions and sufficient fuel a motorist can reach just about any location on a public road. But if the visitor were walking, the situation would not be so funny. Rather than suggesting that the destination is generally inaccessible, it could mean, “You can’t get there, at least not on foot.” It is tragic rather than comic that certain groups of people cannot reach a desired destination because of limited travel choices.

References And Resources For More Information

Access To Destinations (www.cts.umn.edu/access-study/links/index.html) is a comprehensive research program by the University of Minnesota’s Center for Transportation Studies (CTS) to develop practical methods for evaluating accessibility for transportation and land use planning applications.

Keith Bartholomew (2007), “The Machine, The Garden, and The City: Toward An Access-Efficient Transportation Planning System,” The Environmental Law Reporter News & Analysis, Vol XXXVII, No. 8 (www.elr.info), August 2007, pp. 10593-10614.

Bryceson, Maunder, Mbara, Kibombo, Davis and Howe (2003), Sustainable Livelihoods: Mobility and Access Needs, Report TRL554, Transportation Research Laboratory (www.transport-links.org).

BTS (1997), Mobility and Access; Transportation Statistics Annual Report 1997, Bureau of Transportation Statistics (www.bts.gov), pp. 173-192.

BTS (2001), Special Issue on Methodological Issues in Accessibility: Journal of Transportation and Statistics, Vol. 4, No. 2/3, Bureau of Transportation Statistics (www.bts.gov), Sept/Dec 2001.

Xiaojing Dong, Moshe Ben-Akiva, John Bowman and Joan Walker (2006), “Moving From Trip-Based to Activity-Based Measures of Accessibility,” Transportation Research A, Volume 40, Issue 2 (www.elsevier.com/locate/tra), Feb. 2006, pp. 163-180.

Ahmed El-Geneidy and David Levinson (2006), Access to Destinations: Development of Accessibility Measures, Center for Transportation Studies, University of Minnesota (www.cts.umn.edu); at www.cts.umn.edu/access-study/publications.