- ホーム
- > 洋書
- > ドイツ書
- > Mathematics, Sciences & Technology
- > Technology
Full Description
The rst traf c light was installed in 1868 in London to signal railway, but only later, in 1912, was invented the rst red-green electric traf c light. And roughly 50 years after the rst traf c light, in 1920, the rst four-way traf c signal comparable to our today's traf c lights was introduced.



