In the late 1860s, as London experienced significant growth in both population and traffic, the need for a systematic approach to manage the increasing congestion became evident. This culminated in the installation of the first traffic lights outside the Palace of Westminster. Designed by the engineer J. M. G. McDonald, the lights were inspired by railway signals, utilizing semaphore arms that indicated directions for vehicle movement. At night, these signals were illuminated by gas lamps, which glowed red and green, marking the first formal attempt to control vehicular traffic. The semaphore system allowed police to oversee traffic management during peak hours, reducing confusion among horse-drawn carriages and pedestrians alike.

Though the concept was innovative, the installation faced challenges. The gas lamps required constant maintenance, and the semaphore signals could be obstructed by different factors, resulting in difficulties for drivers. The system was short-lived, as a tragic accident involving a gas lamp explosion ultimately led to the traffic lights being replaced. Despite its brief existence, the introduction of traffic lights marked a critical step in the evolution of urban traffic management and set the groundwork for future innovations in transportation signaling.