About the rumoured express bus 500,
Sengkang Interchange to Shenton Way is 21 kilometres. To Boon
Lay Interchange is another 22 kilometres. Total 43 kilometres.
As an express bus service, it must pick up at least 4 Adult
passengers per kilometre.
This means for every trip, the bus must pick up 172 Adult
passengers.
At Jurong West, city direct 651 pick up around 20 passengers
only. I think the other one (premium something) around 40. Even if
combine both into a new route, the combined loading is around 60
passengers only. Sengkang should be around the same.
Both sides need to top up around 112 passengers to make this
express route have "healthy loading".
One way is to ply Bukit Merah Road, to increase loading by about
50 passengers. And also promenade (Suntec city) area, to increase
by another 50. The remaining 12 maybe can get from Lavender area
(Victoria Street / Kallang Road).
This way is perhaps the only way the rumoured express bus
service 500 can have "healthy loading", and run at 2 trips during
morning and evening peak hour.
Meanwhile, a bus route 43 kilometres long is going to attract an
estimated travel time of 120 minutes.
Considering no one from Jurong West or Sengkang would travel
from one end to another (eg. Sengkang to Boon Lay), maybe it's
better to split the route into two. To have the Sengkang route
terminate at Kent Ridge Bus Terminal, and the Jurong West one
terminate at Marina Centre Bus Terminal (near Singapore Flyer).
The estimated travel time will still be more than 60 minutes,
but not as much as 120 minutes. Better for the driver, and easier
to operate also.