Pedestrian Tunnel Guidelines for a Feasibilty Study 2

[jimaitken]

Does anyone have some guidance on the sizing of the opening for a pedestrian/ bike tunnel?

My project involves building a cut and cover tunnel under an existing road way very close to a busy intersection. It is 200 feet long, and ther is no possibility of changing the existing roadway profile to make the conditions more ideal. The tunnel will have to be constructed to allow traffic to continue to operate with minimal disruption. The road is on a fill section and the tunnel cannot be bored or jacked into place. The tunnel will be built in stages and I think I am going to propose a precast 3-sided culvert to be installed. I am not worried about staging and MOT as I think that will work itself out once I decide the size of the section that is needed.

The only guidance I have is that the minimum vertical clearance is 10' and horizontal opening should accomodate 12'. the pasth has enough of a grade differnce that from the high end, when you approach the tunnel you will not be able to see daylight on the other end and I am concerned that people will be uncomfortable using this tunnel if I size it for the minimum requirements. Are there rules of thumb that relate to opening vs. enclosed length? Are there confined space rules, Ventilation parameters, etc...

Let me also say when I saw the proposal I said a pedestrian bridge was better suited to the location but was told the owner's architect said he envisioned a tunnel and it would serve as a landmark for the area. He did not provide a concept drawing of his vision and is not offering one. IMHO a 12 x 10 hole is not going to satisfy his vision, but the client will not be able to afford much more than that.


Thanks.

Jim

 

[cvg]

go out to your nearest urban golf course, chances are there will be an underpass for pedestrians / golf carts. These are usually dimensioned quite well for a single golf cart or wide enough for several people to walk. Also check out the following site for information on Con-Arch which might be an option.

http://www.con-arch.com/

 

[CarlB]

200' is pretty long. We have lots of tunnels along local bike/ski paths but I think 100' is about the longest. I'd guess they vary from 8'-12' wide and 8'-10' high. The longer ones are lighted. These lights seem to attract vandals. I agree at that length a 12' x 10' could be intimidating and need for ventilation should be investigated.

 

[bridgebuster]

A few years ago I was involved in a tunnel project that had a separate ped tunnel of similar length. 10' vertical clearance seems OK; it you go less, people will feel confined. On the width - it depends on on the pedestrian volume - a planner should be able to help you. On the project I was on, I believe the width was 40' (I'll check on Tuesday when I get back to the office)but this was a corridor from a subway station.

As far as ventilation goes, check NFPA-502 (National Fire Protection Association). From what you describe it sounds like you don't need it.

Lighting, aesthetics, and security are important considerations as well.

 

[DMcGrath]

Don't forget about drainage - water pooling or running through the tunnel will make it even less inviting to pedestrians. Stagnant water in the tunnel = yuck. On a materials side, I have been through a pedestrian tunnel made from corrugated metal arch sections that crossed under both a road and a main-line railway. Does your state DOT have any guidance?

 

[jimaitken]

Thanks for your responses.
This is a feasibilty study so some of the details can be left to final design. I have been trying to get some advice from our planners on this but have had no luck. I have been using the guidance for pedestrain friendly design published by our state DOT. The minimum clearances were taken from this guide, but it was written more for sidewalks and is not very specific when it comes to underpasses and tunnels or about usibility requirements. I have been speaking with our local fabricator for Contech (Conspan Arch) and also asked him the same questions, but he does not have experience with a tunnel this long for pedestrians, and he wants me to spec his product so he is going to tell me what I want to hear.

I had not thought about NFPA requirements and I will take a look at them. Any other suggestions would be appreciated.

Thanks.

 

[ACtrafficengr]

You might want to consult an architect. Their profession is highly concerned with this sort of human factors issue. The ped/bike clearinghouse (

http://www.walkinginfo.org)

might be able to help, too.

Get as much light as you can into the tunnel. For one that long, artificial lighting will be needed. If the road has a median, put in some skylights. A light colored retaining wall, properly placed, could reflect light into the end.

A Conspan might be a good choice. The sharp corners on a regular box would tend to visually lengthen the tunnel, where the radii on the Conspan might soften it and allow it to feel more spacious than it is.

If you don't make the tunnel comfortable and convenient for users, you may have people climbing the embankment and crossing at grade. In one bike/ped class I went to, a video shoewed pedestrians walking across a 6-lane arterial and clambering over a jersey barrier rather than going a hundred feet out of their way to use a ped bridge.

Good luck, and tell us how it all works out!

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[bridgebuster]

The project I worked on had a 60' tunnel width but it was to accommodate several thousand people per hour.

A planner in the office said that about 8 sf per person is comfortable although in some subway systems he's seen 1 sf per person used.

 

[bridgebuster]

Check Page 18-9, which has a graph to provide guidance on walkway widths.

http://www.dot.state.ny.us/cmb/consult/hdmfiles/chapt_18.pdf

Credit goes to ACtrafficengr for his response to a similar post.

 

[jorton]

I'm sorry I'm coming into this so late. We have designed a few pedestrian tunnels. One was 150' long with a 10' x 12' opening. We felt the opening was too small, but the owner didn't want to pay for more. We also worked on a couple of tunnels that were shot down by the public for safety reasons. They felt the tunnels would be too accomodating to muggings or worse.