BIKE: Bikes and monorails

[alan_drake]

Several points.

Elevators are not on a time schedule and would fail badly if they were. 
Keeping a good schedule is the hallmark of a good transit system.

I noted that Copenhagen made a mistake in automating.  Each train has a
"conductor" to help pax, so they are still manned.  The plan was for 98%
on time performance, but actual hit a low of 82% (from memory) in the
first summer of partial operation.  Since then, they have improved that
to the low 90s.  Significant revenue was lost due to the poor on time
performance.

Elevators do not have to worry about colliding with one another since
there is one vehicle per guideway.  A lightly loaded elevator can easily
pass a heavily loaded one.  Another complexity in programming for rail
with multiple vehicles/guideway.

It is frequently noted that evenly spaced trains will soon go to uneven
spacing.  Mathematically this is an unstable system.  Train D in the
string will randomly take 2 seconds longer at a stop (probably do to
randomness in loading).  This means that, at the next stop, that one more
person will "just make it" with the help of another pax holding the door,
increasing the delay to 5 seconds.  Meanwhile Train E has one less pax to
pick up and gains an extra second.

The closure in the gap between Train D & E is now -6 seconds and Train D
is +5 seconds behind Train C.  This will result in an increasing delta in
loading as pax arrive randomly at the stops.  Train D will become
progressively more crowded, with slower loading & particularly unloading
times, as Train E gets closer to D and carries progressively fewer pax as
the gap narrows.

The successfully automated systems typically require a number of years of
trial & error programming to adapt to local conditions.  Typically humans
adapt more quickly than programmers to the variety of scenarios that can
develop.

As for average speed.  The typical transit vehicle is limited in
acceleration and deceleration to what has been called the "Old Lady
Test".  How fast can one speed up or brake without knocking the
proverbial "old lady" off of her feet ?  Jerk (the acceleration of the
acceleration) has to be quite low, and the upper limit on
acceleration/deceleration also has to be low.  For most urban transit
lines, with closely spaced stations, most of the time is spent at stop
(loading & unloading) or accelerating & decelerating.  Little and
sometimes no time is spent at top speed.

The entire concept of "express' vs. local rail lines is to reduce the
number of stops, with the associated acceleration, deceleration and
loading times.  Grade separated NYC subways run express trains in order
to save time.

I hesitate to expand on Dr. Goetz's concept (put words in his mouth) but
I suspect that he ascribes the extra running time to stops for cross
street traffic.  Signal priority can largely minimize but not eliminate
this extra "time cost".  Each route is different, but I would tend
towards much lower time savings on average.  The only track section I can
think of where grade separation might double transit speed is the
CBD/French Quarter section of the Canal Streetcar Line which goes by the
entrance of Bourbon Street and has to deal with a large number of drunk
peds & drivers and an often overwhelmed & chaotic street system.

One thing I like about the Copenhagen system is that there is a high
ratio between doors & square area, allowing for quick loading & egress
(like I have seen remotely on Bombardier monorail).  It appears that the
Copenhagen floor arrangement is somewhat better for fast egress, but that
is a judgment call absent detailed observations.  Knocking a few seconds
off each stop adds up.

Alan

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