The phrase "a key route" is correct and usable in written English.
It can be used to refer to an important or essential path, direction, or method for achieving something.
Example: "The new highway will serve as a key route for transporting goods across the region."
Alternatives: "a crucial path" or "an essential route."
Traces of a key route near Xi'an are still visible.
The players might consider avoiding shaking hands because they are a key route of transmission for viruses.
Tax credits, defined as a subsidy by the World Trade Organisation, are a key route of support for the fossil fuel industry.
What was less apparent was that so had a key route — the one I took thirty years ago — to get out of there.
A key route for military and trading expeditions, it was one of the major avenues for the entrance of Buddhism into China from India.
The experimental data show that oxidative stress may be a key route in inducing the cytotoxicity of ZnO nanoparticles in colon carcinoma cells.
At least a quarter of the amount of 1 was found in aqueous extracts suggesting that leaching would be a key route for its release into the environment.
And because the Iranian team had previously committed to closing the Strait of Hormuz (a key route for international trade) in the event of a U.S. attack, they felt compelled to do so.
Armenia, a nation of 3.2 million, lies in a region emerging as a key route for pumping Caspian Sea oil and gas to world markets, though Armenia has no pipelines of its own.
The intense heat melted the steel beams under the concrete overpass and caused the road, a key route delivering drivers to and from New York City, to sink several feet.
Coalition ministers have repeatedly argued that encouraging more business opportunities in poor countries is a key route to ending aid dependency and should be a bigger part of what DfID does.
