If one has ever driven on the 710, he will realize that there is no space for any more trucks. They already pack the right two lanes densely like a thick moving wall, leaving hardly any space for regular cars to merge onto or off the freeway.
It is no wonder the South Pasadena residents keep blocking the final extension of the 710 from the 10 to the 210, even though that freeway extension would be much more convenient than having to drive through all the residential streets. Nobody would want all the trucks rumbling past their neighborhoods, with the trucks' diesel pollution, noise, and traffic congestion.