Transmission Failure problems of the 2000 Chevrolet Venture

I was in a turn lane when my transmission failed with no warning. I had to call the police to move my car out of traffic and have my car towed to the dealership. I truly feel that this is a major safety concern. I just had the 30,000 mile maintenace work done on it 5 months ago. The dealership said that there was no way to detect this failure from happening. It just " happened". That is just unacceptable for me. I drive my children everywhere in that car and this could have easily been a fatality. I have no assurance that this will not happen to the new transmission that I had to buy. I have owned a variety of cars and I have never had any kind of transmission problem with any of them. Our previous car was a 94 chevy van and we had no problems with it, just your normal wear and tear. I know that I did not cause my transmission to fail. I have done everything that a car owner should do to maintain proper maintenace of this car and still this kind of failure happened. I strongly feel that there must be some kind of mechanical failure within the transmission system itself for this to happen. I would like answers to why this happened. Hopefully this issue can be resolved before a fatality does occur. Thank you.

When on an incline the transmission fails to hold the car when the brake is released, causing the van to roll backwards. This happens on slight inclines. The dealer claims this is normal, but with the 15 other automatic cars I have owned, this has never been the case. This occurs when the car is warm and does not happen when the car is cold. The rolling occurs in drive or reverse on even the slightest incline. Chevrolet has not responded to my inquires regarding this issue. I am concerned that the rolling will cause an accident.

Transmission failed prematurely on the vehicle.