I found a study on this from an organisation called TRL commissioned by the DfT in 2004
Their conclusions found:
Data on bus and coach accidents with pedestrians have been analysed and the range of impact speeds determined.
Mathematical modelling has been carried out in order to determine the effect on the trajectory of the average height male of being struck by a bus and coach equipped with a front mounted rack.
A technical officer from the Vehicle Inspectorate was invited to TRL to offer an informed opinion of the selected coach with the front mounted bike rack fitted.
The inspector concluded that the vehicle failed to meet several safety requirements with the rack deployed.
He also noted that the construction of the rack, and the inevitable protrusions from any bikes carried, had the potential to cause serious impact injuries to pedestrians and other road users.
The vehicles with racks fitted were tested using an adaption of the EEVC pedestrian headform and legform test methods for cars.
The vehicles without the racks have also been tested so that the results can be compared with those obtained with the bike rack. These tests show that modern buses and coaches, of the type tested here, offer good pedestrian protection in much of their frontal structure and give few very bad results.
The child headform test results show that fitting of a bike rack, of the type tested, dramatically increases the risk of life threatening head injuries for children, if they are of such a stature to be hit by the features tested.
Taking into account the under reporting of injury risk when using rigid head forms to test bicycle and rack parts, which produce concentrated loads, the adult head form test results show that the fitting of a bike rack increases the risk of life threatening head injuries for adults if they are of such a stature to be hit by the features tested.
The relative heights of pedestrians and the cross bar of a rack-mounted bicycle mean that it will strike most adult and taller child pedestrians on the chest or the abdomen.
Furthermore, the handlebar end will make contact with the chest of most adult pedestrians and with the neck of the smaller females and some children. The characteristics of the impact and the available biomechanical data were considered to produce an informed estimate of the injury risks from this type of contact. It was concluded that the risks of fatal and serious injuries, from these contacts, were high.
The adult legform results show that the fitting of a bike rack of the type tested here dramatically increases the risk of long term disabling leg injuries for both adults and children, in accidents involving pedestrians.
It was also noted that when the bus was in motion, stowed bicycles tended to sway, sometimes bringing the innermost handlebar closer to the bus windscreen.
Female pedestrian (1.7m tall) alongside the stowed rack:
Female pedestrian alongside the handlebar of the outermost bike: