In order to collect real-time traffic data, highway maintenance agencies install loops on roads that tally how many cars are passing through a given section of road and at what speed are they traveling. California has 27,000 such sensors installed on the surface of state highways. However, the Los Angeles Daily News reported that 9,000 of these (about a third of the total) do not work. The loops in theory should work for decades if properly maintained. However, repeated resurfacing work on highways, copper theft and general wear and tear are cutting down the life span of these devices. Several apps and websites use data received from these loops to properly inform drivers of traffic snarls and help them choose alternate routes so as to not make things worse for themselves and the traveling public.