what determines the correct values for bridge rectifiers?
Would a 1.5 amp 100 volts bridge rectifier be suitable for this job?


More than enough in my opinion. Your LED load determines the current that flows thru the rectifiers and this might be only 100mA (5 x 20mA LEDs with series resistors). 1A diodes are an overkill IMO. 100V is OK but no less - I've read that 50V peaks can present themselves on the tracks when using DCC.

You mention DCC and I know this is an DC power supply with data superimposed (it makes it a high frequency AC square wave) to control the locos and lights. Just make sure that any bridge and lighting doesn't destroy the data signal superimposed on the supply - it's easy to do (I believe) if you have a bridge rectifier and load/capacitor. Killing the AC sq wave reversals is not really possible but screwing the rise/fall times might be a problem to anything decoding the DCC data.

Hey, I'm no expert but I do use DCC control on my model railway and I reckon you have to be a little bit careful. My recommendation is not use a "several micro farad" capacitor directly after the bridge