A lightweight universal panel mat (100, 400, 500, 600, 700, 800, 1100, 1500, 1800, 2005, 2010, 2015, 2020) made of plastic or elastomeric material and having a first section that provides a relatively flat, textured or structured top surface to facilitate movement over the mat and a second section having geometry that includes a plurality of cells having top surfaces that support the first section. The panel mats have first, second, third and fourth sides (110,120,135,145) that are configured to matingly engage or connect to the second, third, fourth and first sides, respectively. The connection can be by insertion or snap-locking of one side to another, or by the use of fastening elements that more securely holds the sides together. Thus, similarly configured panel mats can be connected by interlocking to form a temporary support surface, deck, walkway or roadway. Additional side ramps (2030) and adapters (2050) can be used to facilitate installation of the mats (2005, 2010, 2015, 2020) and access to the upper surfaces of the joined mats.