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Delhi’s experiment with efficient public road transportation, in the form of the Bus Rapid Transit corridor, has devolved into a court battle that pitches the city’s wealthy, car-owning minority against the majority of road users.

The next step may be the highest court in the land. The Delhi government plans to appeal to India’s Supreme Court to keep the corridor car-free if Delhi’s high court, which is hearing the case now, decides that cars should be allowed in the bus-only lanes, an official in Delhi’s Transport Department told India Ink on Monday.

Delhi’s buses are residents’ most important method of transportation in the city of over 16 million. Fewer than 20 percent of road users in Delhi travel in private vehicles, including cars and scooters, while about half of all road users in Delhi commute by bus, according to the RITES Delhi Traffic and Forecast Study. The rest use bicycles or three-wheeled auto-rickshaws, or go by foot.

The BRT corridor, which is modeled after other systems in high-traffic cities like Bogota, was designed to make bus and bicycle travel safer and faster, and encourage travel that does not involve cars. It features a bicycle-only lane and a center lane just for buses.

Whether the corridor, which was completed in April 2008, has been a success depends on which camp you ask. It has saved lives, but it has also increased the travel time for car drivers. Whether it has shortened bus travel times depends on which research you read.

Drivers and their advocates are so upset that they have filed a flurry of court petitions, demanding that the corridor be shut. News coverage in some English-language newspapers, particularly The Times of India, has often been sympathetic to these drivers, calling the corridor a “nightmare” and “ a volcano waiting to erupt.”

An interim court order last week directed the government to allow private vehicles to use the corridor reserved for buses. A final judgment on whether to overturn it altogether is due this month from the Delhi High Court.

According to B.B. Sharan, a retired colonel who is one of the petitioners who wants the corridor open to all vehicles, “only 50 buses plied on the corridor in an hour while the number of other vehicles was 40 to 50 times the number of buses.”

Traffic jams are a common sight on the carriageway next to the bus lane, he said. “It is unfair to give so little space to car users. Not a single car user has started using the bus; nobody has benefited from this,” he added.

Not everybody agrees with his claim.

“The number of fatal accidents reduced from an average of 9 to 10 accidents per year between 2001 and 2006 to 2 in 2009 on the stretch,” said Geetam Tiwari, Professor for Transport Planning at the Indian Institute of Technology, Delhi.

Ms. Tiwari was one of the authors of the report “Delhi on the Move: 2005,” which proposed the BRT concept and was presented to the Transport Department in 1995.

“Fatal accidents involving bicyclists have not occurred in the bicycle lane since 2008,” she added.

Dunu Roy, director of Hazards Centre in New Delhi, a nongovernmental organization, agreed with this assessment. “After the BRT became operational, not only have fatalities gone down dramatically, accidents have gone down too,” he said.

Private vehicle use is rising fast in New Delhi and most Indian metropolises: An average of 1317 vehicles, including auto-rickshaws and scooters, were added to Delhi roads every day during the 2010-11 fiscal year according to Delhi Statistical Handbook 2011, of these 95 percent were private cars and two wheelers.

Soon, Delhi’s roads won’t be able to handle the traffic, transportation experts say, making introduction of systems like the BRT necessary. “The capacity of roads in Delhi will be exceeded by 2021 on most major roads and junctions,” said Ms. Tiwari.

Convincing private vehicle owners to use public transportation remains a difficult task in India. Car-pooling Web sites have sprung up recently, but bus transportation is widely seen as inconvenient, crowded and unsafe for women.

Advocates of the Bus Rapid Transit corridor argue that the interim court decision negates the corridor’s original purpose. “Allowing other vehicles in the corridor essentially destroys the corridor. There is space for everyone, but the concern of minority car users seems to influence the city engineers and traffic managers,” Ms. Tiwari said.

Even research related to the BRT is controversial. Mr. Roy of the Hazards Centre said there are multiple problems with an interim report by the Central Road Research Institute (CRRI), a national research organization, which is the basis of the interim high court order.

The CRRI had conducted a trial run between May 12 and May 23 allowing private vehicles in the bus corridor. In its report the institute concluded that traffic moved faster when other vehicles were allowed in the corridor than when they were barred, but the report did not make note of accidents or fatalities.

“Their report is completely unscientific,” Mr. Roy said. He pointed out that in the Terms of Reference the government asked for comparisons with the BRT corridor and mixed vehicle corridors on other roads. Instead, Mr. Roy said, “the CRRI modified the BRT corridor itself and compared the results.”

Subhamay Gangopadhyay, director of the institute declined to comment on the findings of the interim report and said that he would only speak once the final report is submitted to the Delhi High Court on July 12.

Zubeda Begum, the lawyer representing the Delhi government’s transport department, said that she had not looked at the CRRI interim findings but said that the organization was not an expert on the matter.

Despite the pending legal dispute, the Press Trust of India quoted Sheila Dikshit, Delhi’s chief minister, last month as saying that her government “will commission more BRT routes in the city as a means to promote public transport, as a bulk of passengers were ‘happy’ with the existing facility,” but provided no further details.