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Cars can travel forward while a queue disturbance propagates backward. This page turns an active hazard into a negative shockwave speed using a heuristic: the negative of the sum of fourteen and three point five times reaction delay. A delay of one point two seconds gives negative eighteen point two kilometers per hour. At two seconds, the value is negative twenty-one. The arrow moves farther upstream as that entered delay grows. This is the source rule for the displayed metric, not a measured universal law of traffic. Other metrics come from the number of stopped cars. With six stopped vehicles, the hazardous branch gives at least eighteen queued cars, forty-five percent throughput loss, and ninety-seven seconds of clearance time. With twelve stopped, those become twenty queued cars, sixty percent loss, and one hundred twenty-four seconds. The loss bars grow from forty-five to sixty on one shared percentage scale. These outputs are linked heuristics; showing them together does not independently validate the simulation. The cascade indicator changes from two affected signals to three when the stopped count exceeds ten. The native presets change reaction delay, inflow and mitigation flags; the renderer moves individual vehicles while the metric rules summarize them. Exported telemetry includes the live simulation time and current inputs as well as the queue results. Those fields should be inspected together rather than silently removed to force two runs to match. This lesson describes the existing simulator and does not certify real-world signal timing.