Road bikes with those classic “dropped” handlebars are great, but I don’t think anyone disputes their ergonomic drawbacks; the hunched posture, weight on the palms, and narrow saddles make them seem like Middle Age instruments of torture. That’s one big reason why mountain bikes proved so popular when they first came on the scene some 20 years ago. They were much more “upright,” and the fat tires (in pre-suspension days) meant a much softer, less bone-shaking ride.
But, in your dad’s case, I don’t recommend a mountain bike either聴still too stiff and, in many cases, too many unneeded bells and whistles. The best bike for your father is one of several so-called “hybrid” or “city” bikes. These look much like a mountain bike, but have smooth tires (better for paved streets), an even more upright seating position, and features designed to make the bike as comfortable as possible. A good example is the Bianchi Advantage ($420). It has a light aluminum frame, good-quality components, and both a suspended seatpost and front fork for that extra comfort. Very plush. Another good choice would be Cannondale’s Silk Path 500 ($950), featuring Cannondale’s excellent integrated front shock, a suspended seatpost, and smooth-shifting Shimano components. It’s more expensive than the Bianchi, but if you found one on sale or negotiated a lower price, you’d be within your $800 budget.
Don’t forget, also, that extras will boost the cost of a bike. Helmet, bike shoes (helpful, but not mandatory), a seat bag for spare tubes, frame-fitted pump, and gadgets such as a cyclocomputer (non-essential, but nice nonetheless) can easily add over $100 to the final price.