Tuesday, July 19, 2011

Potential problem with Tunney's Pasture LRT station (and other info from an LRT document)

Mayor Jim Watson announced last Thursday the new plans for Ottawa's LRT project. The city released a document about the technical aspects and further information on the LRT stations. The following are some information tidbits from the document along with my take on it:

Trains will run “3:15 minute service (headway) during peak hours.” So, passengers can expect a three minute and 15 second wait if they just missed a train. This is standard rush hour period service in any city with a subway or an LRT. While rush hour service was mentioned, there was no discussion on the service outside of rush hour. My guess is that trains will run every 5-10 minutes during midday (9 am to 3 pm).

Tunney's Pasture will have side platforms. “Indicators on the entry level will alert passengers which side platform the next train departs from.” I don't agree with the idea of using side platforms for a terminus station. In case you are confused by the term “side platforms”, they are platforms on the side with two tracks in the middle. A few examples of Transitway stations with side platforms are Mackenzie King and St. Laurent. The photo below is an example of a station with side platforms in a Toronto subway station:

A centre platform, on the other hand, is a single platform in the station with tracks on each side. Some examples of Transitway stations with centre platforms include Hurdman and Place d'Orleans. A centre platform in an Athens metro station is shown below:

Under the side platform arrangement, a common scenario that will happen to anyone who will use Tunney's Pasture station on a regular basis is that passengers head down to one platform only to arrive to a departing train. Since this station is an end station, there's a possibility that the next train may arrive on the opposite track which would mean those same passengers must climb back upstairs (or use the elevator), check the “indicators on the entry level” again, and descend to the correct platform. This could pose a challenge to the elderly, the physically-disabled, or anyone who requires a priority seat on a bus. I suggest a centre platform with tracks on each side because it makes it minimizes confusion for passengers.

If the city is insistent on the side platform configuration, they should allow only one platform open for service while the other platform should be used for trains going out of service once it drops off passengers. This would accomplish two things: 1. no one would enter an out-of service train by accident and 2. there would be no confusion as to which platform to step on. The Toronto Transit Commission employs this method at a few of their transit stations. This arrangement makes the most sense to me.

Downtown East station, which is situated at O'Connor street, will be 16 m below surface and passengers should be able to descend from the surface to the platform in about a minute. Rideau station, on the other hand, will be 29 m underground and it should take approximately two and a half minutes to reach the platform. This is expected because the tunnel must be dug much deeper than the Rideau canal.

LRT travel times:
“Based on the current modeling of system operation it is anticipated that the train travel time from Blair Station to Tunney’s Pasture Station will be approximately twenty-four (24) minutes. The time from Blair Station to Rideau Station will be less than sixteen (16) minutes and Tunney’s Pasture Station to Rideau Station will be just over eight (8) minutes.”
These times may be a bit surprising, but perhaps, they are still within reason. The thought of travelling from Rideau to Tunney's Pasture in eight minutes may be shocking to some, but keep in mind that the LRT will travel through a tunnel for much of that time. The train will not be waiting for traffic lights or slowing down for other traffic.

Besides the tunnelling depth, these plans and ideas are probably not set in stone. However, this should still provide a good idea of how the LRT will be operated.


David said...

Perhaps, just perhaps, saner heads are prevailing somewhere so Tunney's won't be the terminus after all and instead the line will be built out to Lincoln Fields or Baseline.

I agree completely about centre-vs-side platforms for terminus stations, but when you look at the big picture it makes no sense for Tunney's to be a terminus anyway. Given its current bus station layout, if Tunney's is to be just another station it makes more sense for it to have side platforms.

GaryJ said...

Longer term, Tunney's in unlikely to be a terminus. So why build it as one now, when in just a few more years the line will start being extended to westward?

Anonymous said...

I am disappointed to again read that the reason that the tunnel must be so deep is “because the tunnel must be dug much deeper than the Rideau canal.” The canal is NOT the limiting factor. The existing O-Train tunnel under the canal was built using Cut & Cover and the ‘roof’ of the tunnel is the ‘bottom’ of the canal. The requirement was that there be 7 feet (2.13m) of navigable water above the tunnel. When the North-South LRT line was being designed, the plan was to again use Cut & Cover to twin the existing tunnel; so it can still be done. Since the water level in the canal is kept at a relatively constant level, there is no reason (from the perspective of the canal) that the top of the tunnel needs to be more than about 3 metres down from grade.

The issue is the two large sewer lines which run on either side of the Government Conference Centre; they are roughly 20 meters down. With the old (pre-Watson) plan, a TBM was going to be used to create the ‘Cross-Country’ route. Because this route passed under buildings, it was going to be fairly deep. Because the tunnel was going to be deep for the foundations, the Rideau Station was planned to go under the sewer pipes. The depth of those sewer pipes and the need to have a ‘buffer’ between them and the station was the reason that the Rideau Station was going to be so deep.

Now comes the new (Watson) plan and the tunnel east of Metcalfe is to be at a depth of roughly 16 metres to the BOTTOM of the tunnel, putting the tunnel about 10 metres below the surface. This depth allows for a 5 metre high concourse level above the tunnel and then all of the normal utilities above that. It still seems to me that the tunnel could be raised a bit more, but I won’t be greedy.

However, now that the tunnel to the east of the Rideau Station is not going to be deep, the next section east needs to be re-evaluated as to whether it also can be raised. There is almost 20 metres of room above the sewer pipes, which would be plenty of room for the tunnel and concourse level. Instead of City Staff trying to tie into the previously planned deep Rideau Station, maybe they should be looking to make that station closer to the surface. In order to keep as much of the old plan as possible, Staff plan to have the train dive down from the Downtown-east Station so that the Rideau Station can still be under the sewers. From there, the train would climb at near its maximum rate, around the big curve, to get to the surface for the Campus Station. We can probably charge a premium if we get the tunnel licensed as an amusement ride.

By looking at the possibility of putting the tunnel and Rideau Station above the sewers, the tunnel will never get as deep as planned which will save wear and tear on motors and brakes; the route will be much flatter. It would also mean that the section of tunnel which is expected to be the most ‘technically challenging’ for a TBM could easily be constructed using shallow Cut & Cover; this is the bedrock valley in front of the Rideau Centre. That trench could also be the launch-pit for a TBM should one be used to bore the large curve.

Eric Darwin said...

Tunney's is just a temporary terminus. It is still possible that the initial LRT line will go all the way to Lincoln Fields at opening.
The reason there isn't a centre platform at Tunney's is the clearance. Under the track is a giant sewer; above it are several bridges. Moving the tracks to the sides of the cut (to allow for a centre platform) apparently runs into clearance problems.

Todd said...

I would have to agree with other posters – Tunney’s with side platforms is a good sign that they don’t intend to keep it as a terminus station for very long. I suspect once they finally deal with the routing for the western corridor planning will proceed quickly to add as much as possible to the route by or shortly after opening of phase 1. If automation is turned on from day 1, your disembark on one side, board on the other side would work well as a temporary fix. It isn’t the smoothest way to manage, but it does help minimize confusion.