The united states and the soviet union avoided nuclear war because they did not engage in with one another. however, both chose to fight wars by providing military assistance to their allies in smaller conflicts.

indirect war,

proxy wars

Explanation:

Indirect war refers to the clash between the US and the USSR in world politics, economy and geopolitical affairs that lasted from 1945, til 1991.

Shortly after the famous meeting in the Yalta Conference, the leaders Churchill and Roosevelt showed some differences with Joseph Stalin which wanted to impose a particular vision in global politics. Since the USSR developed also nuclear arsenal by beginning of the next decade 1950, a nuclear threat arose as  a means to reshape wars. However the arms race led the world in a constant tension that would result in the policy of mutual assured destruction. Since conflict between these two superpowers would result in global perish they went to engage in indirect proxy wars, supporting movements that were compatible to their interests.

The USSR backed up many uprisings and established puppet states in Eastern Europe. The same ocurred in Middle East Asia were nationalists and independentists often resolved to the military assistance to outweight the factions they opposed.  Vietnam, Cuba, are the iconic instances we know and learn frequently.

The US did the same,  often causing political shifts from goverments that turned into dictatorships: Nicaragua, El Salvador, Chile, just to mention a few.

In both cases proxy wars became an arena for fiercful political fights , propagana was abundant and ultimately led to armed confrontation.

the underground railroad (apocope of the metropolitan railroad) is a system of urban trains located within a city and its metropolitan area. it is characterized for being a massive transport of passengers in the big cities, uniting diverse zones and their environs, with high capacity and frequency and in segregated form to other systems of transport. metropolitan railroads are built underground or on the surface, although most systems use mixed models where sections are combined in both modalities.

1 - as a result, the metro tends to reduce car travel for two reasons: first, due to the greater transfer of users from the car and, second, due to the reduction in the acquisition of cars in homes located in sectors near the stations of the metro.

2 -the metro allows to contribute effectively to the achievement of all the objectives of an urban development policy: it improves the efficiency of the city's economy by reducing travel costs and also generates a higher level of activities in the city center, taking advantage of of the agglomeration economies.

3 -it is a clean means of transport, since it uses renewable energy (usually electricity), taking care of the environment and avoiding excessive pollution.