Blockades are often a means for people to let the government know they are being treated unfairly or have a problem with government services. It is a form of lobbying. If the water department has shut off water to a district for 3 weeks ( happens often) the residents will block a major highway with signs. The Yaquis near Obregon have had a highway blockage on 15 for over 6 months. They open the highway for about 10 hours a day. Once Kino wanted a high school and the school board made promises but did not deliver. The residents closed the highway for a day. The unions in Mexico do not need to lobby for anything. A simple illegal strike will usually get action. Typically the employer must give them all their back pay, pay a fee to the union, a signing bonus and mordida for the union boss!
Moisheh