The Trolley Problem: Top-Down 2D Ethical Dilemma

Tracks

People on Track A (straight) 5

People on Track B (side branch) 1

Trolley speed 6 m/s

Live Readout

Set both group sizes, then run the trolley. You can pull the lever any time before it reaches the switch.

Distance to switch

— m

Active track

People at risk now

Net lives saved

How it works

Philippa Foot's 1967 thought experiment, seen from directly above: a runaway trolley heads down Track A toward n_A people tied to the rails. You stand at a lever. Pulling it diverts the trolley onto Track B, where n_B people stand instead. You cannot stop the trolley and cannot warn either group in time.

Utilitarian rule:  choose the action that minimizes deaths
                   pull lever  iff  n_B < n_A
Net lives saved =  n_A − n_active_track   (0 if you never switch)

Two ethical frameworks disagree about what matters once you can see this number:

Consequentialism / utilitarianism — only the outcome counts. If n_B < n_A, pulling the lever is not just permitted but obligatory, because it produces strictly fewer deaths.
Deontology (act/omission distinction) — pulling the lever makes you the proximate cause of Track B's deaths, a new act, whereas staying still lets an existing threat run its course. Many deontologists judge the two as morally different even when the death count is identical, which is why the "trolley problem" and its footbridge variant (pushing one person off a bridge to physically block the trolley — same math, most people refuse) are used to probe exactly where that line sits.

This 2D top-down companion drives the exact same switch-variant math as the 3D scene — same fork position, same smoothstep bend onto the chosen branch, same lever lock once the trolley passes the switch — just viewed from above, where the fork geometry and both groups are easier to read at a glance. Drag to pan the view and scroll or pinch to zoom.

Trolley Safe group At-risk group

drag to pan · scroll to zoom