The United States territory of Guam has no railways, nor does it have a merchant marine. The largest port is Apra Harbor , which serves almost all commercial traffic including cruise, cargo and fishing vessels. There are smaller harbors located on the island (most notably one in Hagatna and one in Agat) which serve recreational boaters. Roads are primarily paved out of a coral/oil mixture. When wet, the oil tends to float to the surface of the roads making them very slippery and dangerous. However, as roads undergo repair and maintenance, a different mixture of asphalt is used than previously, so the roads aren't as slippery as before. This is one of the reasons the speed limit on most of the island is 35 mph. Its main commercial airport is the Antonio B. Won Pat International Airport.