Math Errors Matter

Take a look at this table from the draft Transportation Master Plan:

Screen Shot 2015-10-22 at 8.28.44 AM

KTMP draft October 2015, p. 120

Notice anything funny? As Councillor Stroud pointed out, there’s an adding error. The total cost for transit and roads between now and 2034, the last row, is the important bit. The question the table answers is, what is that total cost if we have a lower or higher target for transit use. Consultants and staff suggest we choose a 9% “mode share.” They say that will produce a total cost of 157 million dollars. However, that is an adding error. The actual sum of the infrastructure and transit rows in that column is 207 million. Which means that, if we were to pick the 15% transit target, and have a total cost of 220 million, we would be spending 13 million more dollars between now and 2034, NOT 63 million more dollars as the chart indicates. Staff and consultants tell us repeatedly that we can’t be more ambitious with the transit targets because the costs jump hugely. Well yes, if you can’t add. Otherwise, as Councillor Hutchison points out, it seems like quite a modest extra investment: you spend more on transit, less on road infrastructure, and the overall extra commitment is 6%.

— Laura Murray

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