Long-suffering Southern Railways commuters have suffered travel misery for months
The two sides held lengthy talks to sort out a long-running row over driver-over trains which sparked a series of strikes and brought chaos for commuters.
Around 1,000 drivers will now vote on the deal, hopefully bringing some relief to passengers who have suffered months of disruption because of industrial action and staff shortages.
The Rail, Maritime and Transport union is still in dispute with Southern over changes to the role of conductors.
Aslef has never been against changes to working methods
Aslef general secretary Mick Whelan
The RMT announced it is to ballot workers on Merseyrail for industrial action over the role of guards.
Aslef general secretary Mick Whelan said he welcomed the agreement which he described as "a significant step forward in addressing the safety concerns of Aslef members on Southern Rail".
He said: "Aslef has never been against changes to working methods.
"Rather, we believe any changes should be negotiated through agreed procedures.
"I am confident this deal can provide a safer and appropriately staffed railway for passengers on Southern Rail and I will be recommending it to our members."
He said about 930 Aslef members would vote in a referendum on whether to accept the deal and ballot papers would be dispatched on Friday, to be returned by 16 February.