A night bus service or owl service is a public transport bus service which operates through the nighttime hours. Many cities operate such services, either in addition to or in substitution for ordinary daytime bus services or rapid transit rail services which may shut for maintenance or due to lack of passenger volumes at night.
Twenty-four-hour rapid transit operation is practiced in some cities, which renders these services unneeded. Night bus service is generally much more limited in geographic coverage than daytime services, there are usually fewer lines and routes may run over entirely different paths to daytime services, or the night bus terminus may be in a different place. Some networks may run longer routes than daytime services, which may use interchanges to reach the same outlying districts. Night services usually also run less frequently.
The difference in services may be prefixed with an "N" for Night bus, or otherwise specially branded compared to the daytime services. Another common way of distinguishing them from their daily counterparts are dark-colored line numbers. Some night services may be provided by virtue of operating some routes as 24-hour services. Some cities apply a different night bus fare structure to the daytime services. Some services may allow users to alight at a requested place of stopping rather than at specific bus stops in deference to passenger concerns about safely walking long distances.
Because of much longer intervals than in daily services, night bus lines often offer guarantee transfers to other lines or transit modes (such as trams). To ease the planning many cities use a central hub where all lines converge at a specific time. This makes the line map of many night services look like a wheel with radial lines to the center and some additional lines connecting the outer ends (or running along a ring road outside of the city center).