Many of today's local rural roads and bridges were built in the late 1800s and early 1900s when farms were small, and farmers needed road access to homes, schools, churches and markets. During the 1920s and 1930s, these roads were surfaced mainly with gravel, and bridges were reinforced to carry six-ton loads. Since then, farm size has increased and the number of heavy vehicles traveling on rural roads has also increased to the detriment of the road system. Farmers are using large tandem-axle and semi trailer trucks, long farm tractor-wagon combinations, and wide combines to travel from farms to fields and vice versa. Farm-supply and marketing firms are using similar heavy trucks for pickups and deliveries. At the same time, revenues to maintain the present system and to reconstruct it to accommodate the changing needs of rural America are declining in real terms. Unless revenues increase or the investment needs decline, the local rural road system will continue to deteriorate.