It's flammable,but lighter than air so it's actually less dangerous if it catches fire than gasoline,as gasoline pools under the vehicle and hydrogen burns straight up into the atmosphere. The best solution I've seen used a "honeycomb" of metal to hold the hydrogen in the spaces in the "honeycomb",it was hard to rupture,lightweight and a pretty good means of storing the hydrogen. A half ton of batteries really aren't the definition of "safe" either,and would nescsitate getting an entirely new vehicle rather than some hose changes and a fuel tank swicth to run your existing car on hydrogen. AND still gives you a lot better mileage and practicality than an EV.