"diminish traffic" is correct and usable in written English.
You can use it when you want to describe the act of reducing or decreasing the amount of vehicles or people on the road. Example: Implementing a carpool system can help diminish traffic on the busy highways during rush hour.
Such an achievement holds the promise of greatly diminishing traffic congestion throughout the country.
In the Old Town neighborhood, some business owners were concerned that giving over a large building to a noncommercial use would diminish foot traffic to adjacent stores and restaurants, Mr. Little said.
Reductions in injury-associated morbidity and mortality have been linked to a variety of factors including adequate pre-hospital care, decreased transportation time to definitive care, reinforced transportation laws to diminish road traffic injuries (RTI), and improved injury surveillance [5, 6, 9].
The news from Chipotle was grave as it continues to be hit by diminishing foot traffic in its restaurants, along with the rising costs of food, especially grain.
Increasing the ease of public transportation would relieve overcrowding on existing routes, diminish above-ground traffic and enhance the city's competitive position within the metropolitan region.
Given the trend toward dispersal of people and businesses in urban areas, it seems doubtful that mass transit will appreciably diminish motor vehicle traffic.
During the late empire, as traffic diminished and city dwellers were replaced by rich landowners, Saepinum went into decline.
Working your way north with a car full of winter gear, the traffic diminishes with each highway exit.
Furthermore, as in the single-mobile-node case, it reduces the number of handovers during sudden reductions in traffic, diminishing the possibility of a handovers when the network has not yet stabilized.
