Otherwise, they could face a ticket.
Although on this weekend, officers were giving warnings than fines.
"Because it's so new here and confusing for some, that's why I issued a warning," one officer said.
It's all part of getting used to the tweaks that happen.
"Almost every day to improve the performance and this was another recommendation we decided to implement," said Rick Sheridan with SDOT.
The intersection is a major choke point for commuters getting to I-5 and routinely ends up in gridlock. SDOT says it's unclear how long these tweaks will stay in place.
SDOT is hiring off-duty police officers during the morning and evening commutes for traffic control and to educate impatient commuters about this and other Mercer Mess changes.
"These changes have been built into the budget itself," Sheridan said. "We've anticipated we would need off duty police officers supporting the project."
Eventually, the lead into this intersection will be an expanded six lane Mercer Street. There will also be a new left turn lane from Dexter on to Mercer.