* Rolling Resistance: Even though the tires are rolling, there's still friction between the tire and the road surface. This is called rolling resistance and is a major factor in friction at constant speed.

* Air Resistance: As the car moves through the air, it encounters resistance. This air resistance increases with speed and becomes a significant factor at higher speeds.

* Internal Friction: There is also friction within the car's moving parts like bearings, gears, and the engine itself. This friction generates heat.

Why the car maintains a constant speed:

While friction is present, the car maintains a constant speed because the engine is providing a force that exactly balances the forces of friction.

* Engine Power: The engine produces power to overcome the friction and keep the car moving.

* Fuel Consumption: At constant speed, the engine uses fuel to maintain power, even though the car isn't accelerating. This is why cars consume more fuel at highway speeds compared to lower speeds, as air resistance becomes more significant.

In summary: Friction is always present on a car, even at constant speed. The engine's power is balancing out the forces of friction, allowing the car to maintain its speed.