Carpooling income taxable?

I work at a large automotive manufacturer that is a one hour commute from where I live. I'm thinking about offering carpooling with myself as the driver and charging up to 3 passengers weekly to help offset my driving costs.

Is this sort of thing taxable? I know that plenty of people drive a friend into work for a fee and I've never heard of anyone declaring it as income.

But with 3 passengers all paying around $75 per week I wouldn't want to get in trouble with the CRA.