If you look closely at the map you will see two highways connecting Durango to Mazatlan. Mexico 40D is the new, modern super-slab. It comes complete with long tunnels and huge viaducts that bridge over the many canyons. It is a toll road which reduces the travel time between these points to less than 3 hours. Mexico 40 is the old highway that was completed in 1951. From Durango, which is on the high plateau at about 6200ft., Highway 40 is a motorcyclist's dream road as it climbs its way back into the heart of the Sierra Madres (9400ft) before dropping down to the coast (sea level). You can guess which one I chose. However, with mountain riding comes mountain weather. Most of the day was 52 degrees and raining which made the day a bit uncomfortable (or as I like to say... toughness training). There was almost no traffic on this road because everyone now uses the new faster route. In fact I only saw a handful of cars over the 5 hours it took me to cross. Even in the rain the views were quite beautiful with rocky bluffs and lush jungle flora. The road winds through many little towns that look somewhat neglected. Boarded up petrol stations and shuttered restaurants that used to serve everyone traveling between these two capitals. No longer. As the road twists and descends towards the coast, the temperature rises. Once reaching Mazatlan it was 90 and my wet riding gear became a steam sauna. I once again crossed the Tropic of Cancer and am about even with the tip of Baja. I really enjoy my trek through Copper Canyon and the Sierra Madre but now it's time to head South.