Public Transport Accessibility Levels (PTALS) are a detailed and accurate measure of the accessibility of a point to the public transport network, taking into account walk access time and service availability. The method is essentially a way of measuring the density of the public transport network (bus stops, rail stations, light rail stations, underground stations) at any location.
The measure therefore reflects:
• Walking time from the point-of interest to the public transport access points;
• The reliability of the service modes available;
• The number of services available within the catchment; and
• The level of service at the public transport access points – i.e. average waiting time.
The current Public Transport Accessibility Levels of the South Los Angeles County highlights a general poor transit accessibility, facing the problem of suburban sprawl in which population density drops, and the distance between any two locations increases. This means that mass-transit systems have to go further and further out of their way to accommodate suburban commuters. Beyond suburban sprawl, there is another factor complicating public transportation: the lack of the infrastructure for it, since cities are designed mainly to accommodate cars and public transport infrastructures are still poor in most of the cities, in particular in suburbs. The result is straightforward and predictable: suburban commuters drive cars.