walking is not more efficient than driving.

calories for a group of four to walk a mile (as opposed to sitting): ~400 [1]

gallons of gas to drive one mile: ~1/25 [2]

the amount of energy used to grow food (not even including transportation) relative to the amount of energy the food contains is about 10:1 [3]

amount of energy in one gallon of gasoline: ~31,000 calories [4]

therefore, amount of gas energy to walk somewhere is 4,000 calories for four people. to drive, it's only 1,240. so driving is 3-4x as efficient as walking!

[1] https://www.verywellfit.com/walking-calories-burned-by-miles-3887154#calories-burned-per-mile
[2] https://www.epa.gov/automotive-trends/highlights-automotive-trends-report
[3] https://blogs.scientificamerican.com/plugged-in/10-calories-in-1-calorie-out-the-energy-we-spend-on-food/
[4] https://health.howstuffworks.com/wellness/diet-fitness/weight-loss/calorie1.htm

@mewmew you included the energy required to produce the energy the walkers used... Should you do the same for the gasoline? Extraction, refinement, transportation... Amortized production of the vehicle. Pollution.

I would think the energy used in building roads would amortize down to nothing, but the valuable real estate taken up by road in some places certainly has a cost. If only considering energy efficiency, consider that folks might not have to walk a mile if things were closer together.