Having worked extensively in the music industry in the past, I would be hard pressed to think that foam insert plugs would be the best option. The issue with them is block all frequencies and distort sound. The best, but most expensive option, would be to get a set of ear plugs made for you by an audiologist. They will make a mold of your ear canal and then you can use interchangeable filters to select the amount of noise you want removed. I have a set and depending where I am at use different filters. -5db &-10db are great for noisy bars or sporting events, -15db would probably be great for accomplishing what the OP is doing, and -25db is good for large night clubs, and live concerts. The -25db would probably also work pretty well filtering out highway speed wind noise. The filters used in these ear plugs don't actually remove/block any frequencies, they just lower the volume. However, the cost is around $120 for a set the last time I checked.
The next best option would be what is being called "high fidelity ear plugs". You can find them for anywhere between $10-$30 a set and I think I've tried just about every set out there. While not as good as ear plugs from an audiologist, some of them out there do a pretty great job of filtering sound and not just blocking everything. I think the best option for the OPs scenario and also probably my favorite are the V Moda Faders. Of the 3 I mention these have the cleanest sound. They advertise a reduction of 12db which should be perfect for driving at just about any speed and still being able to have a conversation and hear music. They're also comfortable for long periods and come with 4 sizes of inserts to match to your ear canal. One of my other favorites is the Sure Fire EP4. Super comfortable to wear for extended amounts of time. Filters out a lot of noise. They're great for concerts. Another I liked was the Etymotic ER20XS. Not as comfortable as the EP4s but I've worn them for entire concerts and they work well. They do not filter out as much sound as the EP4s which I like but the sound quality isn't as "clean".
Just for the record, I have no stake in the game with any of these companies and prefer my plugs made by my audiologist the best but it's hard to justify $120 on ear plugs unless you use them daily. You can find all of the high fidelity options I listed on amazon. I think I paid $20 for the V Moda.