Complex sentence: The rugged terrain, limited riverfront space covered by the route and narrow spans of bridges passing over the highway have largely stymied later attempts to upgrade or widen the highway, despite the road being highly over-capacity; it has become notorious for its chronic congestion.
Split into simpler sentences: The rugged terrain, limited riverfront space covered by the route and narrow spans of bridges passing over the highway have largely stymied later attempts to upgrade or widen the highway. With the road being highly over-capacity, it has become notorious for its chronic congestion.