Vehicles are allowed on the territory of the border crossing point in strictly defined cases according to regulation of 15 December 2006 on border control performer by the Border Guard officers (O.J. of 2006 Nr 238 item 1729) – link to the regulation

http://isap.sejm.gov.pl/DetailsServlet?id=WDU20062381729

Paragraph 11 exhaustively liste the  cases.

 § 11. Border control out of turn is made to:

1)     members of rescue groups and experts, as well as their equipment and aids,

2) members of the crews of firefighters, sanitary vehicles and people involved in the rescue,
3) buses in international traffic making regular passenger services,

4) means of transport carrying live animals, perishable goods * or dangerous and transporting humanitarian aid

- and in other justified cases.

*Perishable goods:

Attachments Nr 2 and 3 to Agreement on the International Carriage of Perishable Foodstuffs and on the Special Equipment to be Used for such Carriage (ATP) (O.J. of 2015 item 667) – link to the Agreement

 https://www.unece.org/fileadmin/DAM/trans/main/wp11/wp11fdoc/ATP-2011_final_e.pdf

1982 Internation Convention on Harmonization of the Frontier Control of Goods is also applied (O.J. of 1999 Nr 103 item 1190) – link to the Convention

 https://www.unece.org/fileadmin/DAM/trans/conventn/harmone.pdf

The annexes to the above Convention contain information that the Contracting Parties shall make every effort to facilitate the movement of goods, in particular through the coordination of working hours of services responsible for quality control and customs services and agreement to carry out customs clearance of perishable goods outside normal hours where their arrival has been previously reported.

In addition, it should be noted that the above only applies to border controls and does not authorize the violation of traffic regulations.