Road upgrades give the stated XP times the number of roads. So 5-6 will give you 111,500 XP if you have 100 roads as industrial allows.
Edited to add - once you hit global, you can build 10 extra roads. So that alone is worth 10*(355+470+470+760), the XP gained from each level upgrade done up to level 5. That is ~20k XP right there, or a level and a half alone.