The Mohring effect is a technical property of transit

Public transport

Public transport is a shared passenger transportation service which is available for use by the general public, as distinct from modes such as taxicab, car pooling or hired buses which are not shared by strangers without private arrangement.Public transport modes include buses, trolleybuses, trams...

 systems demonstrating increasing returns.

In brief, as transit frequencies increase, wait times decrease, demand increases, and transit frequencies can increase again. This is because transit schedules occur over time. If there is one bus an hour, the average wait from the desired time of departure (or schedule delay

Schedule delay

Schedule delay is a term in transport modelling which refers to a difference between a desired time of arrival or departure and the actual time. Despite the use of "delay", it can refer to a difference in either the early or late direction....

) is 30 minutes, if there are two buses an hour, the schedule delay drops to 15 minutes and so on. So the presence of an additional user increases the likelihood of additional service being provided.

The effect was named for University of Minnesota

University of Minnesota

The University of Minnesota, Twin Cities is a public research university located in Minneapolis and St. Paul, Minnesota, United States. It is the oldest and largest part of the University of Minnesota system and has the fourth-largest main campus student body in the United States, with 52,557...

 economist

Economist

An economist is a professional in the social science discipline of economics. The individual may also study, develop, and apply theories and concepts from economics and write about economic policy...

 Herbert Mohring

Herbert Mohring

Herbert Mohring is a transportation economist who taught at the University of Minnesota for many years. He received his Ph.D. from Massachusetts Institute of Technology in 1959....

, who identified this property in a 1972 paper.