Complex sentence: Travelers heading north away from the developed areas are allowed a 45 mph (72 km/h) speed limit, however the southbound lanes on the same sections remain posted at due to development on the western side of the road.
Split into simpler sentences: Travelers heading north away from the developed areas are allowed a 45 mph (72 km/h) speed limit. However, the southbound lanes on the same sections remain posted at due to development on the western side of the road.