<Tr> <Th> Road Class </Th> <Th> Injury Crashes </Th> <Th> Fatalities </Th> <Th> Injury Rate * </Th> <Th> Fatality Rate * </Th> <Th> Fatalities per 1000 Injury Crashes </Th> </Tr> <Tr> <Td> Autobahn </Td> <Td> 18,452 </Td> <Td> 428 </Td> <Td> 0.082 </Td> <Td> 1.9 </Td> <Td> 23.2 </Td> </Tr> <Tr> <Td> Urban </Td> <Td> 199,650 </Td> <Td> 977 </Td> <Td> 0.958 </Td> <Td> 4.7 </Td> <Td> 4.9 </Td> </Tr> <Tr> <Td> Rural </Td> <Td> 73,003 </Td> <Td> 1,934 </Td> <Td> 0.249 </Td> <Td> 6.6 </Td> <Td> 26.5 </Td> </Tr>

If there are no speed limit signs what is the speed limit