as electric or hybrid engines. BRT systems can use trolleybuses to lower air pollution and noise emissions such as those in Beijing and Quito. The price penalty of installing overhead lines could be offset by the environmental benefits and potential for savings from centrally generated electricity, especially in cities where electricity is less expensive than other fuel sources. Trolleybus electrical systems can be potentially reused for future light rail conversion. TransJakarta buses use cleaner compressed natural gas-fueled engines, while Bogotá started to use hybrid buses in 2012; these hybrid systems use regenerative braking to charge batteries when the bus stops and then use electric motors to propel the bus up to 40 km/h, then automatically switching to the diesel engine for higher speeds, which allows for considerable savings in fuel consumption and pollutant dispersion. Overcrowding and poor quality service Many BRT systems suffer from overcrowding in buses and stations as well as long wait times for buses. In Santiago de Chile, the average of the system is six passengers per square meter () inside vehicles. Users have reported days where the buses take too long to arrive, and are too overcrowded to accept new passengers. As of June 2017, the system has an approval rating of 15% among commuters, and it has lost 27% of its passengers, who have turned mostly to cars. In Bogotá the overcrowding was even worse; the average of TransMilenio was eight passengers per square meter (). Only 29% felt satisfied with the system. The data also showed that 23% of the citizens agreed with building more TransMilenio lines, in contrast of the 42% who considered that a rapid transit system should be built. Several cases of sexual assault had been reported by female users in TransMilenio. According to a 2012 survey made by the secretary of the woman of Bogota, 64% of women said they had been victims of sexual assault in the system. The system had even been ranked as the most dangerous transport for women. The poor quality of the system had occasioned an increment in the number of cars and motorcycles in the city; citizens preferred these transport means over TransMilenio. According to official data, the number of cars increased from approximately 666,000 in 2005 to 1,586,700 in 2016. The number of motorcycles was also growing, with 660,000 sold in Bogota in 2013, two times the number of cars sold.At the end