I need to help muffle noise from a very busy road

Laurel? There are several including a variegated one.

Pyracanthia is evergreen, and fast growing. It's also denser than laurel, so may block out more noise, no offense to Spritzhenry. It flowers each summer, and has berries in autumn.

Sorry to be negative on this one, but planting, however dense will make virtually no difference to the noise level from traffic. We had this issue with the local council at our previous property when they cut down heavy planting between our house and the motorway at the bottom of our back garden. We objected violently to this but they were able to provide results of sound tests that proved we didn't have a case. A solid barrier is the only way of reducing the level of noise; at least the planting will reduce the visual impact and it's amazing how that helps to create the illusion that the traffic isn't there.