You still miss the point, that besides the people who work at the casino, there is no reason to go there at a designated time. That changes for scheduled events of course.
Although I think the Seaport is plenty accessible from public transit, and people sitting in traffic are suffering needlessly, that's besides the point. Thousands of people work there and more jobs are being added almost daily. These jobs, like most, have set hours by and large. People show up between 6 & 9, and leave between 3 & 6. This is rush hour generally. Hence the gridlock.
M-F are not typically the big casino days, which is why you find lower table minimums during the week than the weekend, to entice people to come. Weekends on the other hand, are much bigger casino days. During the summer vacation weekends, the highways will suck as always, but this doesn't have the same impact on surface roads as commuter traffic does, as Boston and it's surrounds are the destination. It's just a pass through on summer weekends.
Obviously this is a more urban casino than the CT ones, so it's not apples to apples. But, if the demographics that love to gamble are consistent..... senior citizens and asians seem to love gambling, but also have no problem taking buses in general.... young professionals will got for a good time. Many in groups. Many have no problem with cabs. Still some will use mass transit as available..... College kids looking for a good time or to pretend they are big ballers will go, and have no problem taking the T, I'd guess most would. The suburbanites (non- seniors and asian) are the traffic creators. We'll see how they shake out, but the South Shore/ South Coast folks will have other options such as CT and RI, plus the new Plainville casino. The ones closer to Boston have plenty of T access via. Quincy, Braintree, Milton, and to a lesser extent, the CR (because it's not as convenient for this type of day trip.) So some will be smart and take the T, but a lot will drive.
Metro west will have a good amount of drivers. I-90 and south have similar options to the South Shore/Coast folks, and the closer you get to Worcester, they may be tempted to go to Springfield or Mohegan to avoid the traffic. The North shore and NH folks are the ones really being targeted by this location that will add traffic. Luckily the Orange line offers better access to hopefully catch more north people. The south people might be less apt to use the T because it involves exchanges.
The spacing of the casinos is done to spread the impacts this way. The State benefits by you gambling. They get the same amount per dollar at each casino. They don't care that one is making more money than the other. It's up to the operators to convince you to come to each one over the others.
