When analyzing public transportation access, there are many potential indicators to consider, depending on the purpose and scope. Some of the more common and useful indicators include proximity (the percentage or number of residents or households within a certain distance or walking time from a public transit stop or station), coverage (the percentage or area of the community served by public transit routes or networks, or the density or frequency of public transit stops or stations), affordability (the percentage or number of residents or households that can afford the public transit fares or subsidies, or the ratio or comparison of public transit fares and incomes), availability (the percentage or number of public transit trips or seats that are available during a certain period or time of day, or the ratio or comparison of public transit supply and demand), reliability (the percentage or number of public transit trips or services that are on time, or the average or variation of public transit delays and disruptions), safety (the percentage or number of public transit accidents, injuries, and fatalities, as well as the rate of security incidents) and comfort (the percentage or number of public transit trips that meet standards for quality, convenience, and accessibility, as well as customer satisfaction).