(a) there's no 'average speed' goals.
(b) I didn't have to spend two weeks building it first

I think I'd played an earlier version of this before, so can only assume it was included in some of the Beta's, or even the pre-beta of TM, so I had an idea what to do. THat said I nearly did go bust the second year of game play due to a slight error on my part leading to me having to sell the (then non-profitable) Brewery in order to get enough cash to fix things.
From then on everything wen smoothly enough, and am now at the stage when I've jumped ship from my original company in order to take control of the second one having, naturally done what any deserting CEO would do, and bulldoze the profitable industries, cut the tracks in half. (this totally confuses the AI when the get control) and then maxed out on bonds, share issues, to buy some really rubbish industries.
And before you all cry 'cheat', it's no worse than the insider trading I was doing before I did that...
Anyway, I'll have some more train time booked for later, so will see if my devious little plan works of it it will back fire by plunging everyone into resession!
Hopefully that won't happen before I've managed to upgrade my 'new' company into a money printing machine that can take over everything else...

I generally dislike average speed requirements as well. (And I think in my scenario currently if you spend enough money on option choices you should be able to meet the speed goal without using the spur method, as long as every train isn't hauling 8 loads)