If no bollards, then maybe cutout shipping containers to block vehicle access is the way. Concept is in the image. Needed at multiple points inside venue for segmentation to reduce/prevent acceleration.
New Orleans attack showed that a policeman in a car is not just going to start shooting when an attacker initially starts pushing through with a truck. Not a winning design to place an officer into- keep an eye on the giant party and be ready to unload your weapon in to the face of a driver.
