Probably the opposite. Lowest carbon footprint will basically be fewest extraneous stops. Continuing at speed for 30sec takes basically no fuel than stopping

Probably the opposite. Lowest carbon footprint will basically be fewest extraneous stops. Continuing at speed for 30sec takes basically no fuel than stopping and starting. So Google should mostly be routing people back onto the highways and boulevards that they generally eschew in favor of complex routes through side streets that save minimal time for the complexity added.