Most people, when told their 30 minute car trip would take 1 hour by bus, would not read for 30 additional minutes once they get home, so while reading or using your laptop is worth more than doing nothing, it's worth less than what you'd be doing if you weren't on the trip. All you're doing is cutting your losses. And depending on how you value things, this could very well mean the loss from the time on the bus is still greater even after considering that you can read so it's not a complete loss.

Furthermore, I listen to podcasts in the car. By your reasoning this counts as the driving not being lost time anyway.