Replacing single lane bridges

[jim.cox]

So, a bridge costs about $2 million, and single-lane saves you about $0.5 million compared with double-lane. That's a reasonably significant amount of money to me, and it may be better spent elsewhere in the roading system. So single-lane bridges on low-volume roads seem fair enough to me.

Any one fatal accident at $795000 (refer Tranist EEM2006, cost per fatal, all sites) during the life of the bridge and any saving is gone....

[jim.cox]

And traffic control was a train timetable nailed to the bridge.

And dont get me started on the crazy way they sign single lane brigdes -

Why they dont use a "proper" giveway sign is beyond me.

[sunhuntin]

And dont get me started on the crazy way they sign single lane brigdes -

Why they dont use a "proper" giveway sign is beyond me.

thats why they worry me. i know i understand what it means, but i dont know that joe tourist coming the other way knows. specially on the long ones.

[Ixion]

Any one fatal accident at $795000 (refer Tranist EEM2006, cost per fatal, all sites) during the life of the bridge and any saving is gone....

How many fatals are there a year on one lane bridges? Can't say it's near the top of my subjective list.

[Skyryder]

What is the problem with them ?

I think they are past their used by date. I could come up with a more cynical response tourist related but I think that subject's past it's use by date too. Might be something to do with piles. But lets not go there either.


Skyryder

[Skyryder]

And dont get me started on the crazy way they sign single lane brigdes -

Why they dont use a "proper" giveway sign is beyond me.

Becasue some dumb tourist will look to left and then to their right see nothing coming and proceed in front of a bloody big logging truck.

Skyyrder

[Okey Dokey]

Thank you to everyone for your thoughts and information. JimCox and Bogar, your input about costings, etc was really great.

Ixion raised the point of what is wrong with single lane bridges. I didn't think of this as a good/bad value judgement initially. Although I do see a two laner on a SH as being "better", so maybe I am just splitting hairs.

Our population in NZ has grown and I expect it to continue to grow. A bridge is a long term project; the ones I mentioned in my OP are over 40 years old. These bridges are at the end of their lives, so it is not just an upgrade; it is a job that has to be done. I think a single lane option is a false economy in this day and age.

I am talking about SHs here, not secondary or rural roads. Just want to make that distinction.

I've lived in Europe and North America and I haven't seen single lane bridges being installed in these places. If I'm mistaken, I know someone will correct me! Are we such a poor nation that we still have to consider a single lane bridge as a cost saving option?

The cliche "If a job is worth doing, it is worth doing well" sums up my feelings pretty well.

Thanks again for all the input. It has helped clarify my thoughts on the issue.

[sunhuntin]

there are 2 on the west coast [south island] just south of hokitika. long horrid things with ridges like train tracks across at least one of them. _intense_ told me about them when we met up down that way.

[MotoGirl]

How many fatals are there a year on one lane bridges? Can't say it's near the top of my subjective list.

Considering the placement of some of these bridges, I'm surprised there aren't more fatalities. It's a wee bit silly to put these bridges on blind corners and use mirrors that turn to rubbish when it's wet or frosty.

[Okey Dokey]

there are 2 on the west coast [south island] just south of hokitika. long horrid things with ridges like train tracks across at least one of them. _intense_ told me about them when we met up down that way.

I guess what I was trying to ask is if/when they come due for replacement, will they put in ANOTHER single laner or opt for a two laner. I wondered if anyone had seen a single lane bridge put up on a SH recently.

The ones across the Waitaki are 250m and 150m long.

I think all our SH bridges deserve to be two laners; once they are erected I daresay they won't be replaced for another 50 or 100 years so I wish they would just do it properly in the first place...

[sunhuntin]

the two im thinking of should definately be 2 laned. i was petrified the whole way across. at least one had a layby area that stuck out on the side of the bridge. im picking it was to let other traffic pass safely, but if they are going to do that, why not just make it 2 lane in the first place?

[Okey Dokey]

Apologies for the thread dredge, but I have an UPDATE!

"after a cost analysis and lobbying from the community, the agency has decided to build two-lane bridges."

The article in the ODT goes on to say that the increased cost is not substantial for the two-lane vs one-lane, and it would be a better standard.

Thanks again to the contributors to this thread who helped me construct my submission. I am really happy with the outcome.

Construction to replace the 129 year old bridges "may" start in 2012, so don't expect to see them too soon.

[R6_kid:Me]

It only takes one fatal accident on a single lane bridge to make two-lane bridge financially viable.

[crazyhorse]

There are about 3 one-lane bridges on SH 50 from Hastings to south of Waipukurau, and one of them has a 35km corner as you exit the bridge. This road is heavily used by trucks - milk tankers, sheep trucks, logging trucks etc. Its also the quickest route for Napier people travelling south. So this road is used extensively.

Doubt they will change these bridges....ever! Does make you wonder when you see the volume of vehicles using this road.

And 500k (the difference between the 1 and 2 lane) would hardly make any difference to any roading budget - probably only seal a 100m length of road

[yungatart]

There are about 3 one-lane bridges on SH 50 from Hastings to south of Waipukurau, and one of them has a 35km corner as you exit the bridge. This road is heavily used by trucks - milk tankers, sheep trucks, logging trucks etc. Its also the quickest route for Napier people travelling south. So this road is used extensively.

Doubt they will change these bridges....ever! Does make you wonder when you see the volume of vehicles using this road.

And 500k (the difference between the 1 and 2 lane) would hardly make any difference to any roading budget - probably only seal a 100m length of road

I regularly travel this road...I don't see the one lane bridges as an issue at all. The traffic volume is not particularly high, really. I think I have only had to give way about half a dozen times in many years of using this road.
It all comes down to being aware, I guess.....