This should include a year-by-year breakdown of both capital and operating costs compared with those that would have been incurred under a road alternative.
Dylai hyn gynnwys dadansoddiad o flwyddyn i flwyddyn o gostau cyfalaf a chostau gweithredu o'u cymharu â'r costau yr eid iddynt o dan opsiwn y ffyrdd.