I would highly recommend a ramp. I think it would be nice to have a pet ramp at the entrance of the van for large and/or older dogs to go in and out with ease. The steps on the van are slippery and the steps are too wide for some dogs.
A couple of years ago, I took both my large elderly dogs for a check up. Not being use to climbing stairs, they had trouble getting in and out of the van. My oldest dog fell on her hip and side of her face walking out. Unfortunately, the two staff members who saw her fall did nothing about it. One of them did a face and the other outside of the van just stood there. Neither offered to help before or after the incident. I only take my small dog to the van now so I can at least carry him in.
I would highly recommend a ramp, at least during the time when any dog not use to stairs, especially elderly, needs it.