In Hawaii the fastest flows we've recorded were those of the 1950 Mauna Loa eruption. These were going about 6 miles (10 kilometers) per hour through thick forest. That was the velocity of the flow front. Once the lava flows became established and good channels developed, the lava in the channels was going at more like 60 km/hour!
On January 10,1977, a lava lake at Nyiragongo drained in less than one hour. The lava erupted from fissures on the flank of the volcano and moved at speeds up to 40 miles per hour (60 km/hr). About 70 people were killed.