Honestly the biggest change is the scenery, most of the roads are still “intact” (barring the fact that the whole area is under perpetual construction at the moment), the biggest change to the original layout is the stadium section which even then, it’s either a minor route change or just extends the tail end of the circuit by a few blocks depending on what you want to do.
Even GT2’s iteration was outdated, as the King Dome got blown up around 4 months after it’s release. The viaduct is also now completely gone, but currently the route around it can still be driven if construction stuff is cleared out:
View attachment 1109274
If they develop that area into a park however they can just use the next block east to connect back to Yesler Way (green). Personally I think it would be smarter in general to extend the front straight and U-turn more northwards cuz there’s significantly more vibrant scenery there now, including but not limited to a large Ferris wheel and dockside attractions that would look amazing at night.
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I think having the U at University would make the track cooler from the driver’s perspective, but Union seems more realistic for a “fan” perspective, more seating potential. Also reverse variants would still have the Wheel very visible. It’s just south of the Seattle Aquarium as well.
A further alternative would be to extend another ~quarter-half mile north to go past/through the Pike Place Market:
(Aquarium circled for context)
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The 3D map is still severely outdated (viaduct is still present and is fully operational) but the route passing under on Western has a really cool “tunnel”-like section:
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This would lead straight to the green route in the first picture that reconnects with Yesler.
The next mandatory change for the current reality of Seattle as mentioned at the top is the stadium section. Following as close (location-wise) to the original would require using a 360° left handed on-ramp to get on Royal Brougham and split the stadiums and eventually reconnect to Alaskan Way. They could use some of those nearby ramps as spectator opportunities as well:
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The other option is to go further South to Edgar Martinez and go around the Baseball field:
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Taking Brougham logically would finish out the circuit by going up 1st and then taking a switchback/chicane to reconnect to Alaskan Way. Martinez would take you all the way to Alaskan Way, overpassing the south exit of the 99 tunnel, and allowing for a DT-style death chicane where the ramp returns you to the main avenue. In my eyes the Martinez route is more realistic as it avoids the weird tight 360 on-ramp between the stadiums, and could still go up 1st route if the overpass on Alaskan is too skinny.
Seattle would absolutely remain familiar unless PD go for a completely different route somewhere else in the city.