Six unpaid tickets triggers sanctions at the Secretary of State's office.
Now that might change to three. From the Associated Press:
The state Legislature has approved a bill that would make it tougher and more expensive for motorists who pile up unpaid parking tickets to get their driver's licenses renewed. The Senate passed a bill by a 27-11 vote Tuesday that would lower the number of unpaid tickets needed to prompt sanctions from the Secretary of State's office. The bill already has passed the House so it's on the way to Gov. Rick Snyder. Motorists now are blocked from getting or renewing their driver's licenses if they have six or more unresolved parking violations. That number would drop to three unpaid parking tickets under the bill.
The AP reports in 2018, the law would expire and go back to six unpaid tickets needed for sanctions.