The most economical choice is walking. It costs nothing, is healthful, but it is time consuming. The average person can walk about 4-5 miles per hour, so this trip would take at least 10 hours to complete. That means I would probably have to spend the night somewhere along the way. If I have to spend money for a hotel, then this choice really isn't free. Plus, I might arrive at the end tired and with sore feet! After walking comes animal transportation. In my area, horses are not common, so it wouldn't be a likely choice. I believe that a 40-mile trip would take 2 or 3 hours on a horse. If I had free access to a horse, the cost would be minimal. Of course, I'd have to know how to ride!
With a car, the travel time is minimal (under one hour), with only the cost of gasoline to consider. However, I don't own a car, and car rentals are expensive. Shared taxis are one form of affordable transportation, with 4 or 5 people sharing the cost of a car trip to a common destination. The only downside is finding people to share the fare with me. Fortunately, I live in an urban area, where there are buses and 'trains to ride. One of these would be my first choice.
In short, the kind of transportation depends on how fast I need to get to my destination and how much money I have. If I need to get there fast, and money isn't important, I can hire a private taxi. Since I don't own my own car, I don't have that option, and I have never walked 40 miles in one trip. I usually depend on the bus and trains, and would do so in this circumstance. They are cheap, dependable and reliable.