My gameobject movement is slightly jumpy... why?

Hi,

I have cars moving across the screen (similar to crossy road), and in order to move the cars from A to B, I am using:

transform.position = Vector3.MoveTowards (transform.position, RightLaneEnd.position, speed Time.deltaTime);

But, it seems that as the car is moving across the screen, it is not 100% smooth. It seems that the speed changes and jumps slightly. Not LOADS, but enough to ruin the game.

The reason I didn't use the animation feature (which would be much smoother) is because I needed a random speed value to be selected for the cars.

Many thanks, Farid