40% of traffic is for petrochemicals, which according to this article is coal, oil, gas, and things derived from them, which would include fertilizer and plastics and probably some other stuff too like industrial lubricants, asphalt etc. Not just fossil fuels, so not all that 40% would be affected by a switch to renewable energy. It's also worth noting that building out renewable energy generation involves shipping a lot of hardware around the globe as well.
Do we know what the percentage is after subtracting out things derived from fossil fuels? I looked at the article and tried to do the math, but it seems like the stats are bundled together.
Don't forget that if those other things which are derived from them are reduced too that would be a massive win for the health of the planet and everything living on it. Without primarily consuming the fuel component of petrochemicals I think it would drastically change the economics of producing the derivatives and make them scarcer. It looks like a win-win.