Speed: 1-3
1 + 1d6
Speed: 4-6
1 + 1d8
Speed: 7-10
1 + 1d10
Speed: 11-13
1 + 1d12
Speed: 14-17
1 + 2d8
Speed: 18-20
1 + 1d20
Speed: 21+
1 + 1d20 + 1d6; +1d6 for every 2 additional speed