$1.5m buys big improvement in traffic flow at Blue Water Bridge - stacking, staggering booths

June 23, 2012

2012-06-23: Michigan DOT staff at the Blue Water Bridge (BWB) in Port Huron are hopeful they'll have happier customers this July 4. That's the deadline set for contractor Dan's Excavating to have six new primary inspection booths ready for US Customs and Border Protection (CBP.) As at other border crossings the main source of congestion has been backups from CBP inspection lanes - either because the booths are understaffed, or too slow, or there just aren't enough of them.

As an interim measure at the Blue Water Bridge Michigan DOT is 'stacking' and 'staggering' extra booths to allow more motorists to be attended to at the one time within the same plaza pavement area.

The $1.5m project saw work begin early April to 'stack' three additional booths in Lanes 10, 11 and 12.  That involves doubling up booths one behind the other in the same lane.

During construction the lanes were closed so the plaza suffered a temporary reduction in capacity to inspect, and worse than normal backups - 15 to 20 minutes. By the end of May the the double stacked lanes opened, Memorial Day having been the target.

Janet Foran of the MDOT communications office said she traveled through not long after the opening and the 'stacked' booths made a big difference. Since then they've been working on three 'staggered booths' - three new booths in a small line 'staggered' beyond the main line of booths and fed by a single bypass lane. 

A booth previously in the bypass lane has been lost to provide access to the three new staggered booths, so the net addition is 5, meaning that the US Plaza now has 13 primary car inspection booths versus 8 before.

Extra inspection is for cars

There are five primary truck inspection booths as before. CBP booths will have gone from 13 to 18.

Foran says the project should increase the capacity of the plaza by 30% when it is fully open for the July 4 holiday. And she's hopeful motorists will see a real difference with shorter quests and quicker transit times.

Summer is the peak season in these northern parts as people drive up from the south to enjoy the cooler climate.

Once thought 600 vehicle/hour/booth

Primary inspection booths like cash toll booths have usually been thought to have a potential throughput of about 600 vehicles per hour - difficult cases are sent on to a secondary booth to keep the primary line moving. Since a travel lane has a throughput of 1,600 to 2,000 vehicles an hour the rule of thumb is you need three lanes or booths per travel lane.

But actual throughput of inspection lanes seems in these days of islamist terrorism to be well below the 600/lane/hour rule of thumb.

The Blue Water Bridge has three travel lanes each direction so a capacity over the water of 5,000 to 6,000 vehicles/direction. With 13 booths that's about 385 to 460 average/booth.

At 18 booths it becomes 280 to 335/booth.

Of course those stacked and staggered booths can't be expected to work as smoothly as a regular line of booths. Stacking two booths in a  single lane necessarily keeps one inspector waiting for a vehicle ahead to clear before the one behind can move, and there will be times when the forward booth is idle because the lagging booth position is occupied and blocking  vehicle moving in.

The staggered line works better but has its own disadvantages in constraining merge space for the lanes in the regular booth line.

Stiil, they're hopeful the nearly 40% increase in booths will increase capacity by 30%.

Other projects nearby

There are lots of other shortcomings for traffic flow. Just west of the Plaza there has been a serious bottleneck with an old 4-lane bridge over the Black River where long-distance traffic, local traffic and close ramps generate weaving movements. This is the northern and eastern end of I-69 and I-94, and traffic here is often connecting with Canada's H402. And local Port Huron traffic crosses the river here too.

The 4 lane Black River Bridge is being replaced by a 9-laner.

The inspection plaza itself has to be rebuilt and this has been in planning and studies for about 12 years. The planning process was apparently complete with a FHWA record of decision in May 2009.

Little more has been done however because neither MDOT nor the US CBP have the $200m+ needed to go into construction. A pared back version seems the likely result.

BACKGROUND: the Blue Water Bridge is the second largest US-Canada bridge in volume of trucks (4,000/day) after the Ambassador Bridge (7,200) because the two routes are very competitive on the long hauls from Chicago and Indiana through to Toronto and Montreal.

The Peace Bridge in Buffalo is the leader in cars (13,100) followed by the Ambassador Bridge 12,700, Detroit Windsor Tunnel 10,100, Blue Water Bridge #4 at 10,000/day.

In total vehicles BWB is #3 at 14k after Ambassador 19.9k and Peace Br 16.6k.

Traffic peaked at the Blue Water Bridge at 6.14m (16.8k/day) in the early 1990s and has trended slightly down the past 20 years to 5.12m now (13k/day.) Truck traffic was much higher in 2005 than now  - over 5,000/day. It dropped to 3,500 in 2008 but is barely back to 4,000 now.

Interestingly the Blue Water Bridge now carries less traffic on two spans of 3 lanes each than it carried on one span of 4 tight lanes in the early 1990s.

Inspection congestion

Traffic densities on all the US Canada bridges is very low measured by average daily vehicles/bridge-lane compared to bridges on the east coast as the table nearby shows. On the east coast it is normal for bridges to carry over 10,000 vehicles per day per bridge lane.

By contrast on the US-Canada border 5,000 or less vehicles per day per lane are normal - the only exception being the 3 lane Peace Bridge, and even it has a lightly trafficked deck compared to the interstate bridges. Yet there is more serious congestion at the border than on the more densely traveled east coast interstate bridges.

The explanation seems to be that the border they suffer inspection congestion, not bridge congestion. And at the Blue Water Bridge at least they're acknowledging that reality with work at the inspection plaza.

TOLLROADSnews 2012-06-23

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