Just as in the case of concessioned buses, no fare adjustments are conducted regularly, and when increases happen, these are quite significant and are not expected by the population. This has increased political pressure to keep tariffs low, as social protest arises each time a substantial increment is implemented. A December 2013 survey of underground users showed that 56% of respondents agreed with a fare increase from MXN 3 to MXN 5 if the government could guarantee a decrease in crowding, waiting times, delays in service, as well as improvement of trip conditions, such as air conditioning and improved safety (Mitofsky, 2013).52 This fare increase was implemented in 2014. However, public faith in its ability to realise the promised improvement has been dented by major events, such as the need to stop operations of the newly constructed Line 12 (due to the acquisition of unsuitable trains) and the collision of two trains in May 2015 (El Economista, 2015). In the case of the underground, the gap between real and actual fares meant a loss of almost MXN 12 000 million in revenues in 2012.