A guide to going under 3 hours
If you Google search you can find several timing splits calculators.
I printed out the following two charts from this website, stuck them back to back, and carried them in my pocket during the race.
Having the times by kilometre already printed in front of you means you don't have to worry about doing Math in your head, especially as exhaustion starts to take hold.
A word of advice - sticky tape over the entire card with clear sticky tape / laminate / cover it in transparent wrapping. Your sweat, and also occasional spills of water / sports drink and other hazards can make the ink run otherwise.
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Copyright 2007-2010 Michael Milford