When a new route opens without a kink. An Evidence Press briefing. When traffic planners model a road network, they usually assume that every driver takes a cheapest route, given everyone else's choices. This is called a Wardrop equilibrium. It is selfish routing, and it can waste time compared with the best possible plan. The ratio between the two is called the price of anarchy. Planners track total travel time and the price of anarchy as demand grows, because they show when congestion starts to bite. As demand grows, new routes become worth using from time to time. In 2024, Cominetti, Dose and Scarsini proved that at such a moment the slope of these curves moves in a predictable direction, and asked two questions. First, while the set of cheapest routes stays the same, do traffic flows change smoothly with demand, even for the standard road-delay formulas that are flat when a road is empty? This paper shows that they do, on any network, except possibly at zero demand. Second, must the curves show a kink when a new route switches on? The answer is no. A network of just five links, with the standard quartic delay formula, has a new route that switches on with no visible trace: total travel time keeps four continuous derivatives. The trick is two parallel groups of roads whose delay curves touch very closely at the switching point. Five links are the fewest possible, and bigger networks can hide the switch even better. But such hidden switches are exceptional. The slope never jumps the wrong way, and for almost every choice of road free-flow times it does jump. For practice, a hidden switch moves only a tiny trickle of traffic, far below the accuracy of a typical assignment run, so watching individual link flows reveals it sooner than watching totals. A test on the Sioux Falls network found only ordinary, visible kinks. This is an anonymous, AI-assisted, unrefereed candidate, not peer reviewed or independently reproduced. Published on 22 October 2026, its paper and evidence are linked from the Evidence Press release page. This briefing uses an AI-generated voice and is not additional scientific evidence.