A trending video posted to Reddit on Monday appears to show a man holding on to the outside of a Regional Transportation District bus while it traveled along U.S. Route 36.

The video posted to r/boulder has more than 1,300 upvotes and dozens of comments and shows a man hanging onto the back of the RTD AB2 bus. The route travels from Central Boulder to Denver International Airport.

The video drew mixed reactions, with some Reddit users expressing concern and others joking about overcrowding on buses, ticket prices, and transportation access.

One user, identified as r/Impressive-Ad-9540, said:  “They are sometimes full and u have to stand,” referring to the buses.

Another user, r/the-harrekki, joked: “Maybe that will convince them to add more buses to the AB lines.”

According to an RTD spokesperson, the transportation agency “is aware of a video circulating online showing extremely unsafe behavior, and the RTD Police Department is fully investigating the matter.”

RTD’s Customer Code of Conduct prohibits activity and behaviors that may adversely affect the use, operation or occupancy of RTD vehicles and facilities. Customers are required to safely use RTD vehicles and prioritize safety whenever they are on RTD property for the safety and well-being of themselves and others, according to the agency.