Specifically, it is while at a gate, potentially blocking traffic (because I don't remember all the gate codes, I keep them in 1Password). It's not while actually driving, but close.
The implication of:
> with one hand while trying to drive
is that your other hand is on the steering wheel actively driving. It sounds odd to say that one is "trying" to idle while parked at a gate.
Give him a break! Commenting on HN using an iPhone while driving is hard enough and now you want him to proofread?
Gate codes might be more appropriately stored on a piece of paper that you keep in your car or with your keychain.