Assessment of Passenger Security in Paratransit Buses - (2005) 63 page report by Andrzej Morka, Leslaw Kwasniewski, and Jerry W. Wekezer.
Crashworthiness of Forward-Facing Wheelchairs Under Rear Impact Conditions - 2007 study by the University of Michigan Transportation Institute.
Developing a Wheelchair Marking and Tether Strap Program - 2008 study into making securement of mobility devices faster, easier, and safer by Douglas J. Cross.
Oversized/Overweight Mobility Aids: Status of the Issue - 2004 report regarding transportation of wheelchairs that exceed ADA standard.
Center of valuable research including wheelchair crashworthiness and securement, occupant restraint, and WC19: a voluntary industry standard for wheelchairs used in motor vehicles.
Ride Safe - Vehicle safety information for people who use wheelchairs.
Status Report on the Use of Wheelchairs and Other Mobility Devices on Public and Private - 2008 report offers thorough study of current trends and practices.
Use of Rear-Facing Position for Common Wheelchairs on Transit Buses - 2003 study describes this international practice on large buses and identifies pertinent issues relating to it's transferability to the U.S. context.
WheelchairNet - Online community that serves the information needs of anyone interested in wheeled mobility. Includes a section on transportation resources.