Air carrier pilot reported a near miss with a fast-moving tug during taxi. Pilot applied brakes to avoid a collision.

Narrative

After landing in ZZZ at night; we received ATC clearance to taxi via 1 and 2 to the ramp. After turning left onto 3 and establishing a taxi speed of approx 10 knots; the taxiway bends to the southeast. I noticed a tug coming at a high speed (estimated at 30-40 mph) on a road from our left. When I realized he wasn't slowing; I came to a fairly abrupt stop. Immediately after that; the tug noticed us and also came to an abrupt stop onto the taxiway about 20 feet in front of us; at our 1130 position. Then he reversed all the way back (approx 100 feet) to the stop sign; which we presumed he never stopped at in the first place. My first officer's attention was diverted to other ramp vehicles at our 2 o'clock; who appeared to also be heading to cross in front of us. Had I not noticed the tug from the left; it very likely would have collided with our aircraft.I recommend that we include this hazard in our company pages; due to the unique nature of how [taxiway] 3 bends immediately before the intersection with that road; which makes it difficult to notice vehicles who may be coming from the left.