Verbal Reasoning!

[Legate of Amon Lanc]

Okay, I looked it up, and it says:

But King Arvedui held out upon the North Downs until the last, and then fled north with some of his guard; and they escaped by the swiftness of their horses.
For a while Arvedui hid in the tunnels of the old dwarf-mines near the far end of the Mountains, but he was driven at last by hunger to seek the help of the Lossoth, the Snowmen of Forochel.

Since the North Downs are about half way from the Misty to the Blue mountains (and maybe a little bit closer to the Misty), and there are not any Mountains mentioned earlier (just "Mountains"), we can only speculate what Mountains these were. But I was always under the impression that it was the end of the Misty Mountains, or the Mountains of Angmar, because to get to Ered Luin, Arvedui would have to cross Lune and before, go around - or through - Emyn Uial, which doesn't seem logical because he could as well flee to Mithlond and not complicate the matters any more. But we are also told about "swiftness of horses", and going through or around Emyn Uial on horses is not much of a bonus, however on the vast plains between North Downs and the Misty Mountains (or mountains of Angmar) the horses could use their speed well, as later were by the Witch-King himself in his pursuit by Glorfindel.
Also, there is some strange sort of mountains or hills depicted on the LotR map just west of the mountains of Angmar, and since it seems unlikely that the King will on his flight willingly get near the enemy's capitol of Carn Dum, the Dwarven mines could as well be there.

EDIT: Cross-posted. Hmm...