In the early days, a KTM train jouney on the Butterworth-KL sector took something like 9 gruelling hours with the slow mail train making umpteen stops along the way.
For kids, every trip was an adventure. The most eagerly anticipated events were the encounters with the 4 tunnels of Bukit Berapit. Two long and two short ones. (The British were clever not to have made it Three Long and Two Short, 三長兩短). If I remember correctly, the second tunnel south of Taiping was the longest of the four.
With the opening of the new twin-tunnel in conjunction with double tracking and electrification, these tunnels (and tracks) would probably fade into history or else be reclaimed by the jungle. There are some proposals to preserve them…will there be new light at the ends of these tunnels ?