Kansas Turnpike embarks on its largest bridge rebuild

Kansas Turnpike Authority has embarked on its largest rebuild project, letting a contract for new bridges over the Kansas River in Lawrence and reconstruction of interchanges and a toll plaza on one side. Project cost is around $140m of which construction is $113m. The existing steel truss bridges are 52 years old - they go back to the original construction of the Turnpike - and are judged in need of replacement. This portion of the Turnpike built therough the northern part of the city of Lawrence is designated I-70. Lawrence is just 58km (36 miles) west of downtown Kansas City, the major metro area.

The existing twin bridges on the Turnpike at lawrence provide 2 lanes each direction with minimal shoulder. The new twin bridges will each provide a 17.1m (56ft) deck.
First a new span will be built to the north to temporariiy accommodate 2+2 lanes to take all the traffic.

Then the existing spans will be demolished including piers, and the second span will be built in its place.

Once traffic is using both new bridges there will be three 3.65m (12ft) travel lanes each direction and breakdown shoulder each side of the roadway of 3.05m (10ft).

New construction is steel plate girder on 12 spans, the longest four spans over the river being 76.2m (250ft), the others spanning the flood plain and a railroad track. The plate girders reach a maximum depth of 2.36m (93 inches).

Average daily traffic on the bridge is 29.3k, not enough by itself to justify third lanes per direction. But the deck width of 17.1m (56ft) provides redundancy in case one bridge has to be taken out of service. It also allows for future growth.

And to some extent the third lanes serve as an auxiliary lane for traffic entering and exiting the interchanges on either side of the river.

The work involves widening approaches to the bridge, new loops and interchanges and one one side a new toll plaza.

One of the interchanges is being rebuilt with a roundabout intersection at the bottom of the ramps. It takes the long doubles and triple trailer LCV trucks operating on the Turnpike.

Other aspects of the work:

- river width max 208m (680ft)

- construction 39 months June 2008 to Sept 2011

- project length 3km (MP202 to 204)

- bridge length 705m (2315ft)

- engineers HNTB, bridges Finney & Turnpiseed

- project manager Rex Fleming


The Turnpike recently opened another 3+3 lane section - 20.3km (12.6 miles) between East Topeka and Lecompton.

BACKGROUND: Kansas Turnpike is 380km (236 miles) of mostly 2+2 lane expressway extending from the western edge of Kansas City west along I-70 to Tokepa where it angles southwest as I-335 to Emporia, where it becomes I-35 going to Wichita, and then due south to the Oklahoma border. Within Oklahoma I-35 heads for Oklahoma City.

Toll revenues in 2007 were $78.2m on an average 91k trips per day. The Kansas Turnpike does tolling based on trips issuing tickets on entry which are handed to the toll collector on exit. Except at the ends of the Turnpike there are therefore side toll plazas.

Transponders with the brandname K-TAG do 40% of transactions. They are qbn passive backscatter Amtech transponders similar to those sold in Oklahoma and Texas but there is no interoperability with other toll systems.

Measured by exiting vehicles, average daily transactions at the toll plazas are ranked:

Eastern Terminal 14.4k

Topeka I-70 12.4k

Wichita I-135/I-235 9.4k

Southern Terminal 7.7k

Trucks with five or more axles do 9.3k trips/average day and constitute 10.2% of traffic. But the trucks pay $26.5m or 36% of toll revenues.

The Turnpike in 2007 did 2285 vehicle-kms (1420m veh-miles) split 80.2% passenger cars and 19.8% commercial vehicles.

Excluding discounts and adjustments passenger cars paid an average 4.1c/mile (2.5c/km). Commercial vehicles paid 11.6c/mile on average (7.2c/km).

Passenger trips are an average of 39.7 miles (63.9km) while commercial vehicle trips average 63 miles (101km).

The whole of the original 380km (236 mile) Turnpike was built in 22 months opening October 1956.

Kansas is a small state by population with a total of 2.76m people (2006).

http://ksturnpike.com

TOLLROADSnews 2008-05-30