Antimatter is a completely different story.

The difference is that antimatter annihilates with any normal matter that it comes into contact with. This means you can't just put it in a tank, the way you can with hydrogen. You can't e.g. combine it with some metal to make a metal hydride to make it safer to store, the way you can with hydrogen.

At an absolute minimum, you need extremely strong magnetic confinement and an extremely hard vacuum. And even then, you're going to get collisions with stray atoms and annihilation events which release gamma rays and other radiation products - although shielding is probably the least of your worries in this scenario.

A typical research lab at a university or large corporation can't make a vacuum strong enough to store even tiny quantities of antimatter for more than a few minutes, and they can't produce the magnetic confinement strength required to store macro quantities of it, either.

So the question with an antimatter-powered car is not if it's going to destroy the surrounding region and bathe it in hard radiation, but how many milliseconds (or less) it will take before that inevitably happens.

But probably luckily for us, this is all moot, because we have no way of producing enough antimatter for this to be an issue. If all the antimatter that's ever been created by humans annihilated simultaneously, only scientists monitoring their instruments closely enough would notice, because it's such a microscopic amount.

Edit: for perspective, you'd need about 7 billion times the 92 antiprotons transported in the truck in the story to produce the energy produced by a single grain of gunpowder.

You can easily put it into an antimatter tank ;-)