The extent of the subsidy is an issue. The cost of one motor vehicle traffic lane, wide enough for 2 lines of bikes to go in each direction, is a lot less than the price of a road with one lane and shoulder in each direction. So, yes, let's subsidize / pay for / the % of the roadway improvements that we need, and let the cars and SUVs and over-weight trucks pay for the extra width and extra support they need.