National Capital to the Ocean needs an elegant & efficient bridge - P3 potential (EDITORIAL) Posted Fri, 2008-08-29 17:10
EDITORIAL: America's national capital region with a population of over 7.5 million people needs an elegant and efficient bridge on the way to the Atlantic coast. The existing pair of troubled, obsolete and ugly spans called the Chesapeake Bay Bridge need to be phased out, and a modern bridge put in their place.
On the existing decrepit spans there's always some huge disruption. In 2005 it was a deck repaving project that was botched and required months of lane closures. In 2007 it was a spectacular collision after a trailer came unhitched during two-way operations on the 3 lane span, killing several people and stopping traffic for more than a day. This year it's a fall-asleep driver wandering into the path of a tractor-trailer - also in unprotected two-way operations - which instead of being contained by the heavy concrete parapets effortlessly punched through and ended up in the Bay, the driver killed of course.
This Labor Day weekend and for perhaps another ten weeks only a single lane of the southern span will be in operation. After the latest fiasco they discovered corrosion in the steel bolts which hold the parapets to the deck - a 1980s add-on gone awry. Emergency repairs will occupy a lane around the clock.
It will be a maximum 2 lanes open per direction on a 3+3 lane road on either side.
Smaller incidents create less dramatic delays every few weeks.
The present spans are an operational nightmare.
The operational problems of the spans derive from:
- their incompatibility with the approach highways on either side 3+ 3 lanes going into 3+2 bridge lanes
- the lack of deck space on both spans for a central median barrier let alone for breakdown lanes and workzones
- steep grades up from the shallow water structures to the shipping channel spans
- the age of the spans especially the southern span, 56 years old, designed to much lower than current weight loadings and traffic densities
Without providing for greater traffic volumes than now the new Bay Bridge needs to have deck sufficient for:
- three travel lanes each direction to match the approach highways on either side
- sufficient spare space on either side of the travel lanes for broken down vehicles and work space
- a configuration that allows for two-way traffic on either side of a moveable/temporary barrier
Ideally there should be a sufficiently gentle vertical profile to the new bridge to allow heavy trucks to maintain speed on the upgrade but otherwise the deck needs to provide for an extra climbing lane on the upgrades.
About 138 feet (42m) of deck in total or 69ft (21m) each direction is needed to satisfy these requirements, which are normal on new interstate standard construction.
69ft (21m) allows for:
- 3x12ft (3.66m) fullsize travel lanes and 16.5ft (5m) each side for breakdown and work space, and space for runners & cyclists' lanes
- 4x12ft (3.66m) fullsize travel lanes plus 10.5ft (3.23m) each side for breakdown and work space, if the approach highways either side should be 4th-laned
- 6x11ft (3.4m) tight travel lanes plus 2ft (0.6m) central barrier for temporary or emergency 3+3 lane operations if the other direction was out of action
The 69ft (21m) each direction compares with:
- the 1952 southern span 2-lane deck of 28ft (8.5m)
- the 1973 northern span 3-lane deck of 38ft (11.6m)
The present deficient pair of spans provide 66ft (20.1m) total deck width compared to a needed 138ft (42m).
In an area that hurricanes very occasionally reach, and in an age of terrorism our new ideal Bay Bridge should probably built as twin spans - identical twins for esthetics.
The first new span is needed on the southern side to provide a regular 3 lanes eastbound. This would allow the 1952 span to be retired from regular use. It could be kept for occasional use or for regular use by bike riders until it needed to be removed to make way for the second new-span.
The project is not especially challenging in engineering terms. The sea floor is similar in profile to the sea floor under the east span portion of San Francisco Bay Bridge - minus the severe earthquake dangers. The two bridges are similar in total length.
The Maryland establishment - the Transportation Authority, legislators of both political parties, the governor and former governors, the Baltimore Sun - all say a new span is unaffordable.
It's one of the most affluent metro areas in the world and it can't afford a modern, comfortable road to its coastal playgrounds? This is preposterous.
What they mean is a new Bay Bridge can't be accommodated within the budgets and ways of doing things at state agencies.
The state toll authority MdTA doesn't want to take it on.
It's probably best that they don't. They have some big new projects on the go already - ICC and I-95 HOT lanes north of the Baltimore tunnels. Their management of the Bay Bridge has been so consistently awful a great cheer would go up on both sides of the Bay if the bridge was taken away from the MdTA.
The new Bay Bridge will almost certainly be a self-financing toll project.
There's an easy way to find out.
Set up a process to find out from investors what they'll fund in return for the right to toll. It's a perfect P3 or concession project.
Finally the existing spans are an esthetic atrocity that mar the beauty of the Bay with their trashy complexity and their jarring lines, so out of respect for the beautiful Bay we should be looking for ways to be rid of them while building a functional substitute.
(SOURCE: Data here mostly from Bay Bridge Transportation Needs Report, Maryland Transportation Authority, December 2004, which is a useful source of carefully assembled data but like every MdTA study on the Bridge wimps out when it gets to recommending needed improvements.)
Sunday, August 31, 2008
New MD Bay Bridge Needed