This is more common than you think and I believe, under the facts as presented, that this is a viable case against the owner and driver of the vehicle. The first issue is that since the car did not hit the person, can the person sue the driver of the car. Since the car caused the cart to knock the person down, you certainly would be able to sue the driver of the car. The second issue would be is the driver of the car at fault. Under the facts as presented, it would appear the car is at fault. I would expect the car to argue that the the pedestrian was partly at fault, for failing to get out of the way or something to that effect. The last issue would be of damages. If the person fell to the ground but was not injured, then obviously there would not be a case. However, if the person was knocked to the ground and there was some resulting injury (hospitalization, scars, etc.), then there would be a case.