Assuming you're on PC:
Go to arrstatus.com and get an IP, open CMD.exe, type in "tracert <ip>" and see where the problem is; an abnormally high ping on one of the waypoints of your route can be that problem.
You can try using VPN services, like WTFast or other. WTFast is what I used during "high congestion" times at the start of the game, it might help you as well.