What happened to you is not atypical. After midnight the police are on heightened awareness to look for drivers that are intoxicated. They need some excuse any excuse to pull someone over to check for being drunk or drug possession. In some cases they get it right individual is over the limit, in other cases they find something else.
The citation is similar to a ticket, it will however list the violations and contain a court date for a hearing. It appears you will be cited for littering, speeding, and your license plate cover.
Here is what you are looking at:
PA Vehicle Code, Title 75, Chapter 37 - litter and waste dropped, thrown or deposited from a vehicle onto a road right-of-way Penalties: considered a summary offense, imposes a fine of not more than $900, depending on where the dumping occurs, and/or picking up and removing litter from public or private property.
From the PA Fine Card going 90 in a 65 MPH Zone $82.50 See:http://www.justdrivepa.org/Resources/Pennsylvania%20Traffic%20Violation%20Fine%20Card.pdf
License PLate Cover $100.00
Section 1332 of the Vehicles Law : "It is unlawful to display on any vehicle a registration plate which: (1) is so dirty as to prevent the reading of the number or letters thereon at a reasonable distance; (2) is obscured in any manner which inhibits the proper operation of an automated red light enforcement system ... ; (3) is otherwise illegible at a reasonable distance or is obscured in any manner. ...
(c) Penalty for obscured plate.--Any person who violates subsection (b)(2) commits a summary offense and shall, upon conviction, be sentenced to pay a fine of $100.
Court Cost $125.00
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