Possible Clues:

• Fast road, fancy, blocked by stone: no place to remount
• While underway
• It'ss as far as one can be from the bank
• At halfway point in current term, maids get drunk
• Perfectly halfway from either bank
• Inadvisable place to change horses
• Tide's beginning to stop mermaids swimming in current location
• No place to 4?
• Furthest from the banks
• Crossing river, changing team's dim here