Annex 6 Limitation of Conventional Bus Priority Lanes: Case Studies


The BOLs in Seoul were implemented in an effort to improve bus operating speeds and avoid congestion. Over 76 kilometers of median busways were constructed in 2004, (with plans to expand to 162.4 kilometers), making this city a world leader in the use of median BOLs. Over 5,000 buses have installed GPS tracking technology to ensure improved customer service and 815 buses have been converted to operate on natural gas. A smart card system is utilized to allow free transfers to different transit services.

By adding more and more routes and buses to the main median busways, these started to suffer severe traffic jams from 2004. Even with overtaking lanes, commercial speed started to drop dramatically as the slowest vehicles determined the overall running speed. To relieve this problem in rush hours, the city government changed bus lanes on 16 routes, removing 4 Blue Bus and 12 Red Buses routes in July 2004. As a result, the reported average speed rose about 11kph to 17.6kph.

Source: Sam Zimmerman, World Bank

Figure 1 Congested Busway in Seoul

Source: ITDP (Karl Fjellstrom)

Figure 2 Gangnam Road Median Busway in 2005

This can be seen in the figure from 2005. Despite the overcrowded busway, there are still many other buses using the Gangnam Road corridor. However, the lessons learnt from this experience showed that even with the overtaking lane designed to facilitate the correct positioning of bus units, and a wide median platform for passengers (so the total ROW needed in about 15m), there is a practical upper limit to the number of routes and buses that can operate in a median busway.

Current maximum capacity is 12,500 passengers per hour per direction (pax/h/d, ITPD 2008), which, given that further units only reduce operating speeds, can be taken as the maximum for a well-organized 15m ROW median busway with limited overtaking.

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