Description

Traffic Jam is an open transport experiment. Hollow circles attract people, roads constrain their routes, and limited space turns demand into queues. Every person is a persistent individual: the same dot waits inside a destination, leaves, follows a route, arrives, and eventually chooses somewhere new.

Instructions

• Destinations: choose a size from 1–10 before placing a circle. Its size stays fixed: each size unit gives six spaces and one unit of attraction weight. A size-10 destination is ten times as likely to be chosen as a size-1 destination when both are eligible alternatives.
• Roads: choose Build roads, click a destination to start, click empty ground for any bends, and click a destination to finish. No road is committed until it has a destination at both ends. Every crossing, T junction, or shared segment becomes a real graph connection; this map has no bridges. Duplicate overlapping segments share one road.
• People: add individuals using the number field or + buttons. They start in destinations with free capacity; excess people wait in the arrival bay until a space opens. They choose among other destinations with probabilities proportional to size, including full or disconnected ones. An unreachable person waits for you to connect their intended destination.
• Routes and traffic: before departing, each person takes the shortest available route by road distance. Traffic uses right-hand lanes, fixed free-flow speed, a following gap, and no overtaking. Intersections use first-come-first-served all-way stops, one crossing at a time, with exit space required before entry. Full destinations make arriving people queue outside. Dense networks can gridlock.
• Urgency: set the destination stay to any whole number from 1–20 seconds. This changes how often people decide to leave, without changing their travel speed. The new stay setting also applies to people already dwelling.
• Edit and inspect: Move destinations pauses the simulation while you drag a circle. Connected roads stretch with it, and people keep their identities. New roads also preserve existing people and refresh routes. Trips affected by a network edit are excluded from the travel-time comparison; new trips use the new network. Inspect people highlights a dot and its planned route.
• Try an experiment: the optional Bottleneck example sends many journeys through a small central hub. Try adding direct roads between the outer destinations, or increasing the stay time, and compare queues, throughput, and trip efficiency.
• Shortcuts: D destinations, R roads, M move, I inspect, P pause, Escape cancel a road, Backspace undo its last bend. Clear city explicitly starts a new population. Step 1 s pauses and advances exactly one simulated second so you can study a queue. Switching tabs freezes simulation time.

This is a simplified queueing model with all-way stops, rather than a full vehicle or traffic-signal simulator. Map edits update routes without changing the size of existing destinations.