There’s nothing flawed about basing a projection only on conservative estimates. Conservative estimates are less extreme; if less conservative estimates were used, we have no reason to think that gridlock wouldn’t occur as quickly.

The two options are mutually exclusive — doing nothing, by definition, cannot happen at the same time as adopting the mayor’s plan. So the author isn’t assuming the options are mutually exclusive.

The author never made any predictions about what occurs after ten years. So this possibility isn’t something that undermines the author’s argument.

The argument concerns how to accommodate projected increases in automobile traffic. The author never cited to economic concerns or reached a conclusion about economic concerns. So the failure to address the cost of traffic gridlock is irrelevant.

The author presents only two choices — adopting the mayor’s plan or doing nothing. But there was no reason given for why these are the only two options. This presents a false dichotomy.