Bus service use is in decline in England, according to annual statistics from the Department for Transport (DfT).
While bus use per person has increased by 52% in London over the last 25 years, it has fallen by 40% in other metropolitan areas.
An inquiry into the bus market was launched last month by the House of Commons transport select committee.
During the inquiry, MPs are considering bus service reliability, how services are run, how they are financed and examples of innovation and best practice.
Written evidence can be submitted by completing an online form and sending it by Monday 24 September 2018.
The committee is particularly interested in evidence about how bus services are provided to isolated rural and urban communities and their dependence on services.
It is interested in evidence on the effectiveness of the Department for Transport's bus policies, factors affecting bus use, including reliability, congestion and the effectiveness of bus priority measures.
MPs also want to know about the viability and sustainability of bus services, including the effectiveness of funding, fare structures and public grants, regulations affecting bus service provision and the quality of guidance to operators and local authorities.
Committee chair Lilian Greenwood said: "There are a number of reasons for the sharp decline in bus use in England outside London over the past 25 years.
"Congestion, car ownership, an increase in online shopping, and reductions in local authority subsidies all play a part.
"Our inquiry seeks to gather evidence about the health and future of the bus market."
Buses were a vital lifeline in many communities but with funding streams falling and fares rising, their availability and attractiveness to the travelling public was under threat, said Ms Greenwood.
"A successful bus market can cut congestion, reduce social isolation, help the environment and offer a variety of economic benefits. I would encourage anyone with insight into this sector to submit evidence."
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