Mars and Earth at its closest point are 54.6 million KM apart. However, this shortest distance is not expected to occur until 2287, but as a consolation, almost two decades ago we were as close as 56 million KM. This variability exists because both Earth and Mars do not have perfect circular orbits around the Sun.

In that distance, light takes a hair over three minutes to travel. While the space between Mars and Earth is a vacuum, were it not to be and sound could propagate between uninterrupted, it would take almost four years to go between the two planets.

Now why do I care about this?

If you take the total distance of roads on Earth, it would come up to 62.3 million KM. Humans have built enough roads on this planet that if stretched out, it would easily slap Mars about twice per Martian year.

The thing that I cannot figure out is how much of that distance is paved. World Bank data is consistently too old or poorly defined, and some countries of advanced development (Austria, I am looking at you) do not seem to provide a percentage of what roads are paved versus not. However, some messing with the numbers in the cited reference (which is based on data from the CIA), it seems that 22.6 million KM is a reasonable number.

At 22.6 million KM, that is of course not enough to make to Mars. But, this is where it gets interesting because Venus has a much closer orbit! At its closest, Venus is 0.28 AU or 41.9 million KM away, meaning that we’ve paved enough roads on this planet to get us half-way to our runaway greenhouse of a neighbour.

Although Mercury is the closest planet to us most of the time keep in mind.