Bogotá, the capital of Colombia, had a population in 2014 of 8.75 million. It has experienced significant growth in recent years, due partly to migration from the countryside. “The population shift has created major challenges for Bogotá in the transport sector, including heavy congestion of roads due to the increase in the use of private vehicles and the need for a cost-effective means of transportation for the urban poor.” 
In the late 1990s, Bogotá’s public transport was poor and was not up to the task of coping with the rapid increase of users. It was “described as low quality, with low operating speed, resulting in excessive travel times, high levels of congestion, high accident rates and elevated levels of air and noise pollution”.  The buses produced an annual output of 750,000 tons of atmospheric pollutants and noise levels were above 90 decibels on the main streets of the capital.
Bogotá’s mayor, Enrique Peñalosa, proposed a new bus transport system that would alleviate congestion and be both efficient and cost-effective. Through strong leadership from the mayor’s office, the new public transport system became operational in a relatively short amount of time.
The new transit authority, TransMilenio S.A., was established in October 1999 and given the responsibility of planning and managing the construction of the TransMilenio project and overseeing its operation.
Its objectives were to:
- Transform Bogotá’s public transport system in order to improve its citizens’ quality of life and the city’s air quality, and increase productivity.
- Have an updated system with resources in place to provide transport facilities to more than 80 percent of the city’s population.
The first phase of implementation was completed in 2002, the second in 2006, and by 2012 TransMilenio had 12 lines operating in the city and is now believed to be the world's largest bus transport system.
The public impact
TransMilenio has 12 lines, totalling 112 kilometres, throughout the city and around 1,500 buses operating on those lines. There are about 1.5 million passenger journeys every day.
The public impact has been significant, in terms of efficiency, cost-savings, safety and environmental benefits:
- TransMilenio users are saving an average of 223 hours annually, which roughly equates to a 32 percent reduction in travel times.
- Nine percent of TransMilenio passengers used to commute by private car and now commute by bus.
- In the areas where TransMilenio operates, there was a reduction of 92 percent in deaths, 75 percent in injuries and 79 percent in collisions. Robberies at bus stops were reduced by 83 percent.
- Since the introduction of TransMilenio, air pollutants within Bogotá have decreased by 40 percent.
Public Confidence Good
In the first month after TransMilenio opened to the public its approval rating was extremely high. “TransMilenio is also highly socially sustainable, consistently polling public approval ratings of over ninety percent, making it the most popular public project in Bogotá.” The more detailed breakdown was: “that 49% of the users find the system very good and another 49% find the system good”. 
This approval rating dropped after a few years of operation to a lower level in 2006: “over 90 percent of surveyed city residents rated the system as good or very good during the first months of operation, declining to 76 percent more recently, as the public come to accept the system as a normal part of city life”.  There have been occasional mass protests since then, which indicates that approval is now far from universal (see Alignment, below).
Stakeholder Engagement Strong
The main internal stakeholders have been the Mayor's office, the Department of Planning, and TransMilenio S.A. The project received significant support from stakeholders, such as:
- The Instituto de Desarrollo Urbano [the Institute of Urban Development] (IDU), which was in charge of building and maintaining the infrastructure.
- Local and international consultants, who advised on aspects such as feasibility and the construction similar ventures elsewhere, e.g., in Quito, Santiago and Mexico City.
- The World Bank, which contributed 6 percent of the initial funds.
“Design, planning and investment in the infrastructure of the project was carried out by public institutions such as the Bogotá Mayor’s office, the Fund for Education and Road Safety of the Secretary of Transit and Transportation (FONDATT), the IDU, the District Institute of Culture and Tourism, the secretary for transportation and traffic, the Department of Planning, the secretary of finance, and Metrovivienda.” 
TransMilenio S.A. oversaw the design, planning and monitoring of the system, while managing the other entities involved in the system’s operation. “The operation of TransMilenio is performed by private entities. Each private company was selected through an open and competitive bidding process.” 
Political Commitment Strong
The project was a government and the city administration, through the Mayor’s office, and the initial public investment was USD240 million.
The first decision of the local government was to give TransMilenio a very high priority in urban planning, as the main component of its mobility strategy.
Clear Objectives Good
TransMilenio’s objectives were stated at the outset, but not all objectives were measurable. The goal was to improve the reach and performance of Bogotá’s public transport system and, as a result, the city’s economy and environment and its residents’ wellbeing.
TransMilenio was so successful that it became a model for the rest of the country. “Among other things, it decreased the average travel time by 32%, increased property values along the main line by 15-20%, enhanced tax revenues, created jobs, and improved the health and safety of the community.” 
Policymakers drew evidence regarding the basic ideas and structure of TransMilenio from similar bus transport systems that had been implemented elsewhere in Latin America. “The BRT system in Bogotá is a great example of one city leveraging the experiences of another to implement a new initiative. The structure for this system largely mimicked those of Curitiba, Brazil and Quito, Ecuador. By utilising these previously established systems, Bogotá was able to learn from its peers and implement an organised structure based on a proven business plan.” 
Although the transport systems of Curitiba and Quito were the main influences, the consultants also looked further afield. “Studies were prepared to put the project in place, not to evaluate whether such a system should be implemented or not. Information from other transit systems based on buses was collected through visits to Quito (Ecuador); Curitiba, Sao Paulo and Goiania (Brazil); Santiago (Chile); and Mexico City and Puebla (Mexico), which were very helpful in identifying key elements for systems design.” 
The project was both financially and technically feasible.
The cost was relatively low (approximately one-tenth of a heavy rail transit project). TransMilenio was estimated to have a total capital cost of USD 340 million. “The cost of infrastructure for Phase I of the project was US $5.9 million per kilometre. The initial public investment into the infrastructure totalled US $240 million. The public sector’s financial resources for the implementation of the BRT system came from a fuel tax (46%), local revenues (28%), a credit from the World Bank (6%) and grants from the national government (20%). Half of the 25% gasoline tax levied in Bogotá is used for the continued expansion of TransMilenio.” 
The technical feasibility was addressed by exhaustive feasibility studies, based on close analysis of existing bus transport systems in use in Curitiba and Quito and other Latin American cities (see Strength of evidence, above).
The project managers and regulators both were selected from the Ministry of Transport and from local government. The project is managed by three parties– regulators, managers and operators:
- The regulators of TransMilenio are the Colombian Ministry of Transport, which is in charge of national policies and plans, and the Municipality of Bogotá, primarily the transit and transport secretariat;
- The managers include TransMilenio S.A. (responsible for planning, managing and controlling the system) and the IDU, which supervises the construction and maintenance of the infrastructure. Both entities form part of the municipality of Bogotá.
- The operation of TransMilenio is performed by private companies.
An example of the sound management was the way the city administration changed the method of paying the private operators. “One of TransMilenio’s greatest achievements was the successful implementation of a contract-based system for regulating service operations. Changing the way in which operators were paid from a ‘per-passenger’ basis to a ‘per-kilometre’ basis eliminated the ‘Penny-War’ problem [the high levels of competition between operators for passengers, leading to inefficiencies of scheduling].” 
The reduction in passenger travel time and the impact on citizen wellbeing, car usage, air quality and crime were among the main metrics used to gauge the impact of the project.
For example, a study found that travel time-savings were greater for people in the lower income groups: 18 minutes for the lowest income stratum, compared to 10 minutes for the people in the highest income stratum. Travel time reductions were greatest for the longer trips. “Travel time- savings appear to be central to public acceptance of the service – 83 percent stated that time savings were the main reason for using TransMilenio, and 37 percent stated that they spend more time with their families as a result of the faster commute.” 
All the actors were well equipped to implement TransMilenio, principally the city administration, the IUD and TransMilenio S.A. There was good integration with other methods of transport to support the environment: “the system is highly integrated with the city's expansive bike network”. 
Communications strategies, including media campaigns and several activities for user education regarding the project, were developed by the local government to make the public aware of the TransMilenio.
However, there were protests by the public over the services granted by the project in 2008 and 2012, which showed a lack of cooperation and discrepancies in the interests over the services. “In April 2008, passengers went on strike over the system's service, this time citing overcrowded buses, low frequencies, and a lack of alternatives ... In 2012, there were protests over service on Bogota's bus-rapid transit system, the TransMilenio, quickly escalated into riots in Colombia's capital city."