A spokesman for the National Transportation Safety Board says the agency is sending a team of about 6 to Philadelphia on Thursday to look into crash involving two Southeastern Pennsylvania Transportation Authority trolleys in west Philadelphia.
The team will be looking at collision avoidance technology and federal oversight of transit operators, among other issues.
Authorities say nearly 50 people suffered minor injuries when one Route 10 trolley rear-ended another near 38th Street at about 1 p.m. Wednesday.
A total of 44 passengers were hurt along with the two trolley operators.
SEPTA officials say they aren't sure why the trolleys were so close. Trains typically run about 10 minutes apart.