Tile Chart - Units 1&2
A yellow tile with two small stations can be upgraded to any green tile with one station and the same exits. #69 does not upgrade.
114	To:	15
1	55	To:	14	888
2	56	To:	15	887
A yellow tile with one small station can be upgraded to any green tile with one station.
4	To:	14	15	887	888
3	To:	12	14	15	887	888
A yellow tile with one large station can be upgraded to any green tile with one large station.
5	To:	12	14	15
6	To:	12	13	14	15
Green tiles with stations have no neat summary rule.
Bristol hex	12	13	To:	38
52	To:	64	65	66	67	68
Value-40 russets upgrade in Phase Four.
38	To:	51