Apositive effect of urbanization was the building of which public transportation systems? taxis trolleys buses trains

During the 19th century, American people travelled from one city to another by rail or canal. However, as cities grew faster, transportation infrastructure  developed so as to allow citizens travel within the city much more easily than before. Before the 1880s, the most common means of transport within cities was the horse-drawn carriage known as omnibus. But, this form of transportation was an ongoing problem since horses needed to stop for taking a rest and be fed.

A positive effect of urbanization was the building of the electric trolley which was a public transportation system that ran throughout the day and night. However, as cities became larger and crowds continued to grow, the trolley lines started to be built above the streets, creating elevated trains, or L-trains.

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.

assessment is the missing word