Metro is trying to improve the time it takes for its police officers to make it to the scene of crimes or other emergencies.

It takes Metro police an average of nine minutes to respond to emergencies, the agency says in oversight documents, while it takes other police forces between four and eight minutes.

Around the nation, Metro's response time is more than double that of San Francisco's BART system, which is frequently compared with Washington's transit agency.

"Collectively, deployments of emergency personnel from each department in [Metro] are being reviewed and revised to decrease the amount of time it takes to get personnel on emergency scenes and mitigate the emergency," Metro said in oversight documents provided to the D.C. Council.

Metro has 450 police officers who roam its facilities across Virginia, Maryland and the District. When a rider calls in an emergency, Metro transit police often take the trains to get to the scene, causing the agency's response time to be longer than the D.C. police department's average of just over eight minutes for all calls.

But Metro officials say their response time can't be compared with the city's, since Metro officers have to navigate underground facilities across a wider area.

"Metro Transit Police have responsibility for protecting Metro customers, employees and assets in a 1,500-square mile area (an area more than three times the size of Fairfax County)," wrote Metro spokesman Philip Stewart in an email. "To maintain high visibility to allow for effective response within the transit system, a significant portion of our 450 officers patrol on foot and use transit to respond to calls."

But Metro's response time is also longer than that of the BART system in San Francisco, where officers take an average of four minutes to arrive on scene, a spokesman said. Transit experts often compare Metro and BART, since they both were opened in the 1970s and both have just more than 100 miles of track.

They also have similar police-to-rider ratios. Metro has more than 700,000 riders on an average weekday and 450 officers. BART has about 400,000 daily riders and 200 sworn officers.

Metro is beating one other transit system. A spokesman for the Los Angeles Metro said the officers patrolling its trains take 10, 20 or 30 minutes to arrive on scene, depending on the type of request.

But the response time may not be too worrisome, since experts say response times often aren't linked to catching more criminals or even improving citizen satisfaction with police forces.

"I think that's because by and large response times are pretty fast," said Nancy La Vigne, director of the Urban Institute's Justice Policy Center. "I think that under 15 minutes is a fast response time unless you are lying on the ground with a bullet wound."

Spokesmen for Philadelphia's SEPTA system and Dallas' DART system said they don't track response times. A New Jersey Transit spokesman said his agency doesn't make the times publicly available.