Incas in south America did not have horses; or oxen for that matter. They had  only had Alpacas and Llamas ; which are slow and you have to walk with them instead of riding them.  The Tambo was a service station on long, often mountainous trails. Primarily used by messengers and officials the Tambo was a protection from the storm when in their most primitive form; on busier walking routes they would be larger administrative buildings - some would develop into whole towns.  At the very least all Tambo had cooking facilities and officers called Hikgo would refuel the route with firewood and kindling. 

Tambos were typically built one days walking distance apart. Humans walk at around 3-4 miles per hour; so if we assume that the Incas could walk for 8 hours a day - that would be about 20-25 miles apart.  

The word roughly translates as Inn; so we take it that at a very minimum the Tambo provided sleeping facilities, and these facilities were part of the road network.  On exposed mountainous terrain like this; you can imagine yourself being caught in harsh weather after having been walking for several houses - and the feeling of seeing a wind and water tight structure where you can light a fire and warm yourself up. 

What strikes me about the Tambo is how obvious it is; a network needs nodes to reinforce it; otherwise it is just a sprawling mess and I cannot be alone in thinking that the road networks of today - connected every 50 miles with travel lodges; I see them as quite sparse and barren to those that do not have a vehicle. 

What the tambo shows us is; as our infrastructure adjusts more and more to other engineering; those that are without homes, and cars and phones find it harder and harder to survive. Homelessness gets harder and harder to escape from every time another piece of primitive culture is lost. 

In the UK the Inn; is no longer a budget room above a pub for a travelling vagbond type; and food