Inspired by others I thought I'd build my own little bridge.
I made the ramps a little too steep though and had to glue on some sandpaper so the tank could get some grip!They climb it ok now though.
It's all the wood I had though so I had to make do.
I tried model railway ballast mixed into diluted pva first of all,still not enough grip.
I think you are right that sand would have been better but I was just using what I had on hand at the time.
We like bridges. Great stuff. If you want real grip, pop down to B&Q and buy a roll of the non-slip rubber mat - the honeycombed stuff, and lay that. It is brilliant for gripping anything. I use it in the back of the car when I transport the tanks, it grips the carpet and the tanks and they don't move an inch.