Rivnuts from Homestead, PA on 9/14/2021 9:25:21 AM:
My advice depends on your level of aversion to riding on city streets and sidewalks. First of all, if you are very risk averse, then I would not recommend any of three routes that Google Maps provides when entering Union Station as your origin and the Holiday Inn in Southside as your destination. The shortest Google-offered route is, in my opinion, the sketchiest. That said downtown Pittsburgh traffic is not NYC, Chicago or other major metropolitan city traffic and, with normal caution, can be ridden on a bike.
I'll suggest two different options. The first will minimize the amount of city streets to traverse and provide some scenic views of Pittsburgh and the second would be the route I would choose to ride through town, across the river to and through Southside.
The following is a Ride With GPS map link for the scenic and least/safest city street route. It takes you to and along the riverfront trails along the Allegheny, Ohio and Monongahela Rivers through Point State Park. You can see the Convention Center, PNC Park, Point State Park, Heinz Field the Carnegie Science Center and the Inclines as well as downtown. Also you'll ride right over the medallion citing the beginning of the Ohio River and the literal beginning of the GAP trail. You have to get onto the sidewalk along 11th Street at Waterfront Drive to get down to the riverfront trail along the Allegheny River and ride up the switchback ramp along the Monongahela River to get up to the Smithfield Street Bridge sidewalk. The ride from the Smithfield Street Bridge over to Bingham Street and the Holiday Inn may be challenging to follow but watch for other riders going that way as there is usually a stream of people coming into or leaving town through Southside to help guide you there or just ask another biker. If you've never been to Pittsburgh before, this is the route to take.
The link below is the route across downtown rather than around it. Its shorter but takes you on more downtown streets including Grant Street which is arguably the busiest street downtown. However, you can ride on the sidewalks (Yeah I know its "illegal") and stay off the street itself if you choose. (You won't get arrested.) The route from the Smithfield Street Bridge (sidewalk) to the Holiday Inn is the same as the previous route.
Ok, that's my advice but as always its only as good as it cost. :-)