Its perfect shot. In case of over exposure, decrease shutter speed value in small steps until you get you get a perfectly exposed shot. That's the only thing you can do.
Remember, this control is best used in dim or dark areas, you took the photo in already very bright place.
Assuming ISO was kept on lowest possible value,
Shutter speed,
1 second = less bright photo with little light trails.
5 seconds = moderately bright photo with moderate light trails.
10 seconds = very bright photo with maximum light trails. Suitable for darker areas.
For light trails, choose a darker busy road where there is lots of traffic and use 5-10 seconds shutter speed.
