1.
roadside; along the road; route
The area along the side of a road or route. Commonly used to describe spectators, shops, or scenery along a parade route, marathon course, or similar path.
Usage
沿道 specifically means the area along the sides of a road or route. It is very commonly used in news coverage of parades, marathons, and processions to describe where spectators gather. Compare with 道端 (roadside), which is more casual and refers to the immediate edge of any road, while 沿道 suggests a longer stretch along a specific route.