How do railway signals work?(alpharail.co.nz)
26 points by zeteo | 6 comments
alpharail.co.nz on Hacker News
2 stories on the front page, newest first. Scroll down to watch the site change over time.
Why do railway tracks have crushed stones alongside them?(alpharail.co.nz)
654 points by Twixes | 269 comments
AlphaRail blog post explaining why railway tracks are laid on crushed stone ballast.