Posting this issue here is a good start as you have been able to alert the Transportation, Traffic & Parking Department of the offense. If this was a metered space or a space on a public street we would be able to ticket and tow the offender. You can also contact the New Haven Police Department's non-emergency number at 203-946-6316 as they will also ticket/tow the vehicle. You can also inform the proprietor/manager/owner of the business/property if the space is not on public property. It is always better to inform the authorities of the situation rather than approach the individual yourself.
Thank you for posting this issue.