A fat a$$ scooter in motion tends to stay in motion, unless the fat a$$ scooter is compelled to change its state.
As I ride down Route 53 to the Chicagoland Speedway I have to go over a steel grate bridge. Now these bridges are small and relatively easy to ride over. But a steel grate bridge and 2 wheels are not the best combination.
When scouting out a ride, encountering a steel grate bridge may cause you to change your entire route. Most bridges are not that "long" and can be ridden over easily. How anyone can ride two wheels on the Mackinac Bridge is beyond me. (5 miles long; 199 feet above the water). Maybe if fleeing a zombie apocalypse over the bridge was necessary... if I really needed to mainline some of that fine Mackinac fudge.. then maybe! I hear it can be done, by those with bigger balls than myself!
Any whooo... Riding over a Steel grate bridge is like riding on ice. You just have to make sure you keep your speed constant and let the bike roll you over the grates. Do NOT be afraid. As newtons law states, a body in motion tends to stay in motion. This motion will carry you forward over the grates. You will feel the slip and wiggle of your tires, but as long as you stay calm and maintain a loose grip on the handle bars, you will be fine. A little bit of throttle is okay, to keep your speed up, but gently does it.
Make sure there is plenty of room between you and the vehicle in front of you because you don't want to have to do a quick stop on the bridge.
If you want any practice, the steel grate bridges in Joliet Illinois are a good place to start. These bridges are relatively short and small with a small arc. I went over them about 4 times yesterday. Just for practice...(not really, it was because I got lost and had to go over one bridge twice...DERP!).
These small bridges will give you a wee idea of what you might be up against if you want to try something larger.