<P> Originally intended as a bypass to I - 5 through Seattle, I - 405 has experienced a large increase in traffic volume since its construction . I - 405 is now the most congested freeway in Washington State, particularly the segment between State Route 169 and I - 90 . </P> <P> Currently underway is the Nickel Project, which in 2003 originally included three planned improvements for I - 405: </P> <Ul> <Li> The construction of one lane in each direction between SE 8th and I - 90, replacing the Wilburton Tunnel . </Li> <Li> The construction of one northbound lane from NE 70th to NE 124th, and one southbound lane from SR 522 to SR 520 . </Li> <Li> The construction of one northbound lane from SR 181 to SR 167, and one southbound lane from SR 169 to SR 167 . </Li> </Ul> <Li> The construction of one lane in each direction between SE 8th and I - 90, replacing the Wilburton Tunnel . </Li>

Why is i 405 in washington an interstate