If you plan to reach Dushanbe from north, from Kujiand you have to pass to major mountain ridges.
The northen one is the Shakristan-pass. There is a tunnel. It's 5km long and the northern portal is at around 2650masl. The southern is almoust 100m higher. So it's a clim direction south.
We cycled trough the tunnel. It's totally OK to do that. There is ventilation, light and a concrete street surface. But even there is light inside, turn on your bicycle-light. At least a backlight that the traffic coming from behind can see you.
The old road over the Shakristan-pass is closed because of a mudslide. This information we got from other travelleres and from the military standing there, where the old road goes of the new one.
Getting dowm from the Shakristan-tunnel brings you to Ayni. Some Kilometer after Ayni you will go right over a bridge and then the street follows a breathtaking gorge towards the next tunnel/pass combination at Anzob.
There is a tunnel but it's totally not recomended to cycle trough there. There is water on the ground (10cm or more), almost no light, no real ventilation and a damaged concrete street sruface. All cyclist we met took a car or a truck trought this tunnel. And for some it took almost an hour for this 5km.
Because of this informations we decided to take the other option and went for the old, offically closed, road over the pass.
There where the new road goes crosses the river and goes up to the tunnel we got of the good road and took the pretty small road following the river on the north side. You will pass some smaller villages and before the climb to the pass really starts there is the village of Anzob. We saw some small shops but didn't check them out. We filled our water from a fountain in the village. After the village go over the bridge and short after the street starts to climb.
Anzob is aorund 2100masl. We made it up until 2550masl where we found a very nice place to camp. Its there where the road goes to the western side of the main "stream".
We rode over the pass in middle of July and there were some snowfields left in the last part of the road. But they were melted good enough that at least a meter of the rad was snowfree. When you get to the pass on 3375masl you will see a small farm and a meteostation. We were invited to lunch from the family living up there to do the meteo stuff.
The road surface on the northern side is mostly gravel but good pressed and expect some meters it was driveable for us. Only in the last part with the snowfields it was wet and because of that a bit harder to ride. And there are even some asphalt parts.
The southern side, our downhill, has more asphalt and that's the side where the family living at the pass is coming up with a Lada Niva. It took us almost 2 hours to ride down the aprox. 20km down to the new road coming from the tunnel. I would say it's also possible to ride the pass in the other direction. You have to push your bike probably some meters more but most of the pass should be driveable too.
The hole pass is, from my point of view, a good alternative to the tunnel if you have enough time and power. I think untill something pretty big, like a landslide or so, the contition of the road will stay pretty the same.