paying on board. Use of a payment card which must be touched briefly to a card-reader is also fast. For the system to work, users can receive "credit" on the electronic cards: in this manner, passengers who have no money left on the cards can take the bus at sidewalk stops where there is no possibility to recharge these cards. This means that the balance in the card can be negative, up to two ticket fares, so passengers can take the bus in the street and recharge the card once they reach a main line station. As the card itself costs more than the maximum negative balance, the passenger has no incentive to default on negative credit. Transmilenio in Bogotá followed suit in 2014 also creating routes that can use main line stations and regular sidewalk stations, but instead of giving credit to passengers to allow boarding the bus on sidewalks, published a map readable in smart phones giving the location of a dense network of 4,000 recharging points, located in internet cafes and other business, that use a swipe-card terminal for recharging. This system has the additional benefit of diminishing queues on main line stations. Bus Priority, Turning and Standing Restrictions Prohibiting turns for traffic across the bus lane significantly reduces delays to the buses. Bus priority will often be provided at signalized intersections to reduce delays by extending the green phase or reducing the red phase in the required direction compared to the normal sequence. Prohibiting turns may be the most important measure for moving buses through intersections. Platform-level boarding Station platforms should be level with the bus floor for quick and easy boarding, making it fully accessible for wheelchairs, disabled passengers and baby strollers, with minimal delays. High-level platforms for high-floored buses makes it difficult to have stops outside dedicated platforms, or to have conventional buses stop at high-level platforms, so these BRT stops are distinct from street-level bus stops. Similar to rail vehicles, there is a risk of a dangerous gap between bus and platform, and is even greater due to the nature of bus operations. Kassel curbs or other methods may be used to ease quick and safe alignment of the BRT vehicle with a platform. A popular compromise is low-floor buses with a low step at the door, which can allow easy boarding at low-platform stops compatible with other buses. This intermediate design may