Problem with my accent

I have been having problem with my 2001 Hyundai accent 4 dr. the lights get dim and sometimes just go off in traffic and i need to park my car and accelrate the car for the lights to return and the airbag lights oon the dash board comes up. for sometime now the lights on the dash board battery/brake lights comeson but just dull and in the dark it can be noticed and a while later it goes off, I do not understand what can be the problem with it can someone please let me know what has to be done.

hi
I have been having problem with my 2001 Hyundai accent 4 dr. the lights get dim and sometimes just go off in traffic and i need to park my car and accelrate the car for the lights to return and the airbag lights oon the dash board comes up. for sometime now the lights on the dash board battery/brake lights comeson but just dull and in the dark it can be noticed and a while later it goes off, I do not understand what can be the problem with it can someone please let me know what has to be done.