Ideas Why yellow traffic lights were designed to be ambiguous
Dec 16, 2025
In this intriguing discussion, Travis Stocking, a Senior Traffic Analyst, explains the complexities of amber light timing and traffic signal engineering. Alfred Mele, a philosophy professor, dives into the split-second mental processes behind driving decisions. Ron Usher shares his experience with an automated red-light ticket, pondering the clash of machine judgment against human discretion. Together, they explore the ambiguity of yellow lights, the history of traffic signals, and the challenges of automation in driving decisions, unveiling how our choices can lead to unexpected consequences.
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A Ticket Sparked The Documentary
- Seán Foley describes getting a red light camera ticket that sparked curiosity about yellow lights and decision-making.
- He recruited a traffic professional contact who worked in Intelligent Transportation Systems to explore the issue further.
Purpose Of The Amber Signal
- The amber signal exists to warn drivers in the indecision (dilemma) zone so they can either stop safely or proceed without jamming brakes.
- Proper yellow timing also includes an all-red clearance to allow vehicles to clear the intersection.
The Dilemma Zone Was Mapped Mathematically
- The 1959 GM study formalized the 'dilemma zone' mathematically, showing distances where stopping or clearing the intersection becomes impossible without risky actions.
- Engineers still wrestle with translating that math into real-world timing because driver behavior varies widely.