Many sources claim this road gets its name because it was built by prisoners of war in the 1940's. Or it may be named after it's more famous cousin, the Burma Railway which was built by allied POWs in Burma under horrendous conditions. Nevertheless, the climb to the top is brutal and relentless.
From the A9, a short (~0.7 mi) paved road takes you to a small settlement along the Allt-na-Criche Creek. Veer right at the fork just before the settlement and proceed through the gate. Just after the gate, there is an "honesty box" usually with some tasty traybakes to fuel up for the run.
Thus begins the long (1,400 ft), steep (~10% average grade), arduous (rocky at times) climb. The first 0.5 miles or so is through forest and then you'll break out into open territory. As you climb increasingly higher, the views of Cairngorms National Park to the east improve. You'll want to stop and take lots of breathers, err pictures, along the way to the top.
Initially the road has a smooth gravel surface as it receives some farm traffic but it becomes increasingly rough with larger rocks as you near the top. It's never technically difficult though, just long and steep.
Three rock cairns mark the top of the climb at 2,300 feet and the view from here is impressive (unless if happens to be foggy). If it's a clear day, consider it an omen that you should take the narrow rocky path to the summit of Geal Charn Mor (400 feet additional climbing over rocky singletrack) for true 360-degree views.
Down the other side of Burma road, the road is considerably rockier (larger, looser), but similarly steep in the downhill direction. If you brought a full-suspenion rig, you'll appreciate it on this speedy descent into the tranquil valley of the River Dunlain. After you cross a bridge over the river, the trail turns decidedly north and follows the river for some time and the descent continues at a much more gradual grade.
When you reach a house at the 7.0 mile mark, the trail surface switches to grass for a short distance before switching to crushed stone. This continues to track the river until 10.3 miles, when you should veer left onto a doubletrack. You could continue straight, but sometimes this section is boggy. The doubletrack is a bit rocky but not technical. It takes you to a small farm where it intersects with the NCR7: Sluggan Bridge Off-Road Section
Expect to see lots of sheep along the way and very few people. The summit can be exposed and windy, so mind the weather.