Rehabilitation of railroad and highway tunnels without closing traffic

Enlargement and rehabilitation of railroad and highway tunnels without fully closing traffic is technically and economically feasible using methods that can be used worldwide. over 200 railroad tunnels and several highway tunnels in North America were rehabilitated and enlarged without taking the tunnel out of service by working during short "work windows." These tunnels were rehabilitated and/or enlarged in the last decade, mostly in response to the need for taller or wider vehicles. Enlargement was usually accomplished by raising the crown. Generally, work on railroad tunnels is done from a work train containing all necessary equipment and materials, and which was moved into the tunnel during a work window usually lasting from a few hours to eight hours. Similar decisions and methodology are used on highway tunnels, except that these are usually accomplished by lane closures or nightly work windows.