There are thousands of roads, is there any rhetorical device in the first low-carbon road?

Yes.

It is a metaphorical rhetorical device that hides the ontology of the metaphor (environmental protection) and compares low carbon to environmental protection. Expressing the importance of low-carbon and environmental protection.

A low-carbon lifestyle not only saves personal expenses, but also represents thrifty and hard-working consumption. It also protects the environment and is green consumption.