Accessibility

Accessbility

Definition

Accessibility (or just access) in transportation planning refers to the ease of reaching goods, services, activities and destinations, which together are called opportunities . Access to these locations is the goal of mobility. The ease of reaching these locations is determined by sufficient road capacity and sufficient parking spaces. Are there good options for public transport? What is the average travel time to reach the centre? Accessibility can be defined in terms of potential (opportunities that could be reached) or in terms of activity (opportunities that are reached).

A measure that is often used is to measure accessibility in a traffic analysis zone i is:

$Accessibility_{i}=\sum _{j}{Opportunities_{j}}\times f\left({C_{ij}}\right)$ where:

• $i$ = index of origin zones
• $j$ = index of destination zones
• $f\left({C_{ij}}\right)$ = function of generalized travel cost (so that nearer or less expensive places are weighted more than farther or more expensive places).

A city with a good accessibility has good possibilities to get emergency services to an incident location, or to get people quickly out of the area in case of any danger.

Other meanings

The words accessibility and access can have various meanings and implications.

• Accessibility generally refers to physical access to goods, services and destinations, which is what people usually mean by transportation.
• In roadway engineering, access refers to connections to adjacent properties. Limited access roads have minimal connections to adjacent properties, while local roads provide direct access. Access management involves controlling the number of intersections and driveways on a highway.
• In the fields of geography and urban economics, accessibility refers to the relative ease of reaching a particular location or area.
• In pedestrian planning and facility design accessible design (also called universal design ) refers to facilities designed to accommodate people with disabilities. For example, a pathway designed to accommodate people in wheelchairs may be called accessible.
• In social planning, accessibility refers to people’s ability to use services and opportunities.

Factors that influence accessibility

Transportation demand refers to the amount of mobility and accessibility people would consume under various conditions. Transportation activity refers to the amount of mobility and accessibility people actually experience. Transportation options or modes of transport refer to the quantity and quality of transport modes and services availaable in a particular situation. Improving the quality and quantity of the modes of transportation means improving accessibility.

Sometime, a particular factor significantly affects accessibility. For example, inadequate information or poor security around public transport terminals can constrain public transport use (potential riders don’t know how to use it or have exaggerated fears of discomfort and risk).

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