Congestion has an upside. Electric cars often travel farther per charge on city streets than on highways, reversing the familiar gasoline-car pattern because their motors waste little energy at stops and recover some energy when slowing. Speed exacts its toll. At highway pace, aerodynamic drag rises sharply, demanding more battery energy for every mile even when traffic flows without interruption.
Braking offers partial refunds. Through regenerative braking, an electric motor acts as a generator during deceleration, converting some kinetic energy into electricity instead of letting friction brakes turn it all into heat. Recovery is never complete. Lower city speeds also reduce aerodynamic drag, whose force grows approximately with the square of speed, while the power needed to overcome it grows approximately with the cube. Stops barely tax propulsion. Unlike a conventional gasoline engine that keeps burning fuel while idling, an electric motor needs no propulsion energy when stationary, although heating, cooling and other accessories continue drawing from the battery.
Gasoline rewards steady work. On highways, combustion engines generally operate under steadier loads and in higher gears, reducing the relative burden of pumping losses and avoiding repeated acceleration that ends with energy discarded through braking. The advantage has limits. Higher speeds still increase air resistance, while hybrids, automatic stop-start systems, weather and vehicle design can weaken the usual city-versus-highway contrast for either powertrain. Cold complicates the bargain. Cabin heating can consume enough electricity during slow journeys to erode an electric car's city advantage, leaving the traffic light less a universal blessing than a mirror of what sits beneath the hood.
