I am assuming you are referring to the impacts of the US national road system, so I am using the US as the example in my answer. There are countless impacts of roads and other transportation networks, but I will list just a few here. Because a region's industrial and...
employment base is closely entwined with the quality of its transportation system, two key economic benefits of the national road system in the US have included boosting national productivity and employment.
A transportation infrastructure that is well run and in good condition allows businesses to obtain the materials they need to make their products and then ship goods to market when completed. This gives companies the ability to lower transportation costs, which trickles down to decreased production costs and enhanced productivity and profits. Roadway proficiency and investment also directly impact highway construction industry employment, as a variety of workers are needed to run it efficiently, including managers, specialists, and laborers. Additionally, personnel are needed from supply and manufacturing industries, thereby generating more investments in these areas as well.
Socially, the advent of the road system contributed to restructuring within American culture, increasing mobility and access for people across the nation, connecting cities with small towns by growing the suburban lifestyle and leading to the influx of people leaving home to commute to work. It also gave people more flexibility to interact, shop and socialize in much less time than in the past. On the downside, this new structure led to the destruction and isolation of neighborhoods in many cities, as people fled the cities for the suburbs.