From my trip last December.
Western Sahara. Good road all the way from Agadir to Dahkla. Watch out for the numerous fish blood dumps in laybys which have spread onto the highway. The fish lorries from Dahkla just empty their lorries of blood and melted ice straight onto the side of the road. Could be a slippery mess if still damp (they stink as well)
Dahkla to border. Good road, but less well marked and slightly narrower. Brilliant riding road and less traffic.
Border with Mauritania. 3-4 kms of poor rocky tracks and a few sand traps through minefield. Easy enough though and fun. (Saw a 38 ton artic go through here).
Border to NKC. First 10k good unmarked sealed road. Strong possibility of sand berms, watch out for these.
The new road starts from a junction after the border road crosses the ore train track. Turn right for NDB and an enjoyable time in the town (see the ship wrecks, drink
and eat huge fish at the excellent and spotlessly clean Restaurant Canaria).
Turn left for NKC. If you run on petrol ensure that you have enough for 450k. Last December, no petrol on the road. (have things changed anyone?)
Diesel can be bought from bladders or bottles from various places along the route. There is a also a Diesel station about 50k from the ore train track junction.
The road all the way to NKC is world class brand new, well marked smooth heaven. It's a long stretch though with almost nothing to break the monotony.
Sand gets on the road and the Mauris don't seem to clear it off that fast. So look out for unexpected sand berms.
Some great dune country about two thirds of the way along
NKC to Rosso. Reasonably poor potholed and cracked road. Good enough for reasonable cruising speed, but stay alert for rough patches, holes and ruts.
One 300 metre stretch of missing road about half way along. Smooth hard packed surface though. Occasional bits where locals have dug up chunks of tarmac to repair their roofs.
Turn right in Rosso after fuel station (petrol here ususally) and before the port for road to Diama Dam (100k mixed piste, some soft sand, some corrugations, nice ride great scenery)
Or take ferry from Rosso to stay on Tarmac. Port and border a challenging experience, not recommended.
Diama Dam. Mauri exit a relaxed set of formalities. Pay fee for riding in national park
Senegal border. hundred times better than Rosso. Pay (or not) rip-off 10 euro to get through gate, then immigration, then customs. Carnet essential in my view. Douane guy was friendly and said that he was pleased to see my carnet as he wastes hours arguing with people who don't have them. His words; "no carnet, no entry".
Two camper vans at the border had been there all day and were not being allowed in. The guys in them were waiting to see what would happen.
For me, a quick chat with the Douane, a couple of stamps, ten minutes in total and I'm out of there. Unstressed and ready to enjoy Senegal
Folks do seem to be able to get these Lazzez-Passes, I suppose much depends on the atttude of the customs guy on a particular day. Others can advise on the procedure to get these. For me a Carnet always. Minimise hassle, enjoy the journey. I get enough hassle at home.
Senegal roads to Gambia good and enjoyable as far as Kaolack. Lots of check points all are OK. From there to border mixed. Starts rough, turns to total crap for about 20k and then turns into lovely smooth sweeping country road which seems to be quite new.
Gambian Border, yes they ask for the Carnet, though I understand that it isn't essential. We were on bikes and they wanted it. Plain clothes cops there who get offended if you question their credentials. This earned us a massive search of our luggage and an 'interview'. Nothing unfriedly though, just rather formal. They get very friendly once they're happy with you.
Then hellish disgrace of a road to Barra Port (15k), nervous hour on dangerously overloaded ferry and you're in Banjul.
Roads in Gambia mainly broken and potholed rubbish apart from road to airport from the Altantic coast resorts and the main road south from Banjul. The 2 metre deep pothole on the main road in Serakunda should be a tourist attraction in its own right. Avoid Westfield Junction, Serakunda in the rush hour.
Regards
Craig