First seen in the 1970's as the so-called taxi colectivo (collective cabs), peseros were originally big cars with fixed routes which would pick passengers at any point through their route, and drop them off also at any point. Passenger capacities were limited to those of a large car (usually up to 6 people plus a driver).
Being cheaper than a proper taxi, and able to cover routes that weren't feasible for larger buses or other forms of public transport, by the 1980s pesero owners started using Volkswagen microbus vehicles (known in Mexico as combis) for increased capacity of up to 12 passengers. Due to the lack of government investment in public transport, the demand made them a very good business, and while the owners did keep up with demand by adding more units and routes, particularly in newly developing parts of the city such as Nezahualcóyotl, they did so without much order or regulation. By the mid-to-late 1980s most peseros were converted to gasoline powered, half-length passenger buses (known as microbús or simply el micro in Mexico, although they are not similar to the VW Microbus vehicles mentioned before). There were capable of carrying around 22 sitting people, or up to 50 counting sitting and standing people.
To this day, a fleet of approximately 28,000 peseros (as of 2007) carry an important part of Mexico City's public transport passengers, surpassing by far the capacity of the Mexico City Metro, STE trolleybuses, buses and taxis; peseros, (including VW Microbus, micros proper and full-length diesel buses) carry up to 60% of the city's passengers. However, due to poor regulation, corruption and uncontrolled growth, they have also become a problem, causing pollution and traffic congestion and being a source of insecurity and accidents due to lack of operator training and unit maintenance. The government is seeking ways to regulate microbus operation, such as reducing the number of units or replace them with full-size diesel powered buses which are more efficient, carry more passengers per unit, and can utilize transfers and/or a unified farecard system, such as the system that has been implemented in León, Guanajuato (See: Optibus). Other proposed alternatives include expanding the Metro and STE trolleybus network and different forms of transportation, such as the Metrobús, which has completely replaced pesero travel along Avenida de los Insurgentes avenue, and the Tren Suburbano, which will serve areas north of the city. Unlike most other North American and European cities of similar size, it is not possible to buy a pass or farecard in Mexico City that is valid on all types of transport within the city, rather, each form of transport one boards requires an additional (albeit low, the Metro fare is only MXN 2 pesos) fare. Pesero drivers do not receive a fixed salary; rather, they are required to meet a daily quota prescribed by the owner of the vehicle. The driver is then allowed to keep the rest of fares of the day. This fosters fierce competition among drivers, as every passenger is seen as valuable merchandise towards meeting the quota, and thus increasing the driver's personal profit. As a result, it's not a rare sight to behold two or three battered down peseros racing furiously against one another with complete disregard for the passengers they carry or for other vehicles. Accidents, often deadly, ensue and are fairly common. However, given the lack of any real alternative, they remain in high demand throughout the city.
Currently peseros travel fixed routes, being able to pick up or drop off passengers anywhere through the route (a major source of traffic problems and annoyance due to the sudden and unexpected stops). The fees are according to distance traveled: from MXN $2.50 for a trip of up to 5 km, MXN $3.00 for a 5-to-12 km trip, and MXN $4.00 for a trip of 12 km or more. Routes usually begin in metro stations and end in outlying neighborhoods of the city or sometimes even in municipalities in Mexico State. Typically, less than five pesero routes begin in a small metro station that serves only one line, but this number rapidly increases depending on the number of metro lines going through a station. The terminal station of a metro line usually functions as a transport hub and may be served by tens of different pesero routes. In addition, every major avenue in the city is served by at least one pesero route.
Due to the lack of organization of the pesero network, there is no comprehensive index of routes available to the general public. Nevertheless, routes are assigned a route number in order to distinguish them from each other in license plates. Individual peseros also have a sign affixed to the windshield indicating major points covered by the route such as metro stations (denoted by the Metro logo), hospitals, schools, avenues, etc.