How do they work where you live?
Here in the UK the authority in charge of the work can apply to the government (I believe the Department of Environment) for a Compulsory Purchase Order in order to buy the land, property etc which it needs in order to carry out the scheme. The owner receives full market value and may also receive compensation for upheaval etc.
However, the authority cannot apply for the order until the plans for the proposed work have been finalised and approved. Obviously there is a need for such schemes, but until recently I had not appreciated the full impact on those who may be affected.
A new road scheme is proposed in my area, and the home of some friends will be demolished if the current plan is approved. But the timetable for this work is that finalisation of the plans is expected by Spring 2005 with final approval being obtained by late Autumn 2005. Compulsory purchases will then take place by about Summer 2006.
Just about the time these plans were announced (September 2003), they had decided to move home. The result of the plans is that they are not likely to be able to sell their current home at anything like market value, so they have to wait. And of course if there are any changes to the plan this will just add delays, so they have to wait longer. And at the end of the day the plan may be dropped, so they will have waited for nothing.
Yet the local authority is under no obligation to purchase the house now or to compensate them for the delay, the only compensation will be for the upheaval if the scheme goes ahead.
I am interested to hear what happens in other countries, I doubt it could be much worse than here in the UK.
Edit: We've just voted the councillors primarily responsible for this scheme out of office, but the plan has been drawn up and will no doubt have to go much further until it is approved or dropped.