"We want collective agreements to be signed, and back payments for working people to be paid," said Savas Tsiboglou, head of the Greek Association of Merchant Marine Mechanics, as he demonstrated Thursday morning in Piraeus.Workers have been protesting the abolition of collective wage agreements and planned reforms to the pension and income contribution system. Other measures that took effect this year include a 25 percent cut to the incomes of most public servants, leading to a string of new strikes and protests. Separately, farmers in central Greece parked their tractors along the country's main highway for a second day, under the watchful eye of riot police, threatening to shut the road to protest spending cuts and high fuel taxes. Similar protests by farmers in the past have led to widespread disruption to transport and the supply of goods, with the central north-south highway shut for weeks. ____ Srdjan Nedeljkovic in Athens contributed.