Office of Operations
photos of traffic merging onto congested highway, congestion in snowstorm, variable message sign, cargo, variable speed limit sign in a work zone, and a freeway at night
21st Century Operations Using 21st Century Technologies

Traffic Bottlenecks

Combating Bottlenecks


Calming "The Zoo" and ramp metering elsewhere.

Bottleneck Projects: 1) Additional lanes added to the I-94/I-894/US 45 interchange (i.e., "The Zoo"). At a cost estimated between $200K and $500K, new paving added to the ramps, including an "exit only" lane that did not exist prior, off of I-94 to NB US 45, plus addition of an auxiliary lane on EB I-94 to NB US 45, and an "exit only" lane for WB I-94 to SB I-894. A before and after evaluation was not performed for this work but anecdotal observations indicate a positive return. 2) Beltline ramp meter project. This project installed five ramp meters on the Beltline in 2001 as part of a pilot project. As part of the evaluation, traffic data was analyzed that had been collected before ramp meters (September 2000 to May 2001) and after ramp meters (September 2001 to April 2002). In addition, researchers reviewed 911 incident reports for crash data, conducted CORSIM computer modeling, and conducted before and after opinion surveys of Dane County drivers. In addition, a survey was conducted of transportation and law enforcement agency personnel. The University of Wisconsin two-year evaluation study of the effectiveness of ramp metering on the Beltline found that ramp meters have been effective at improving safety and travel reliability on the Beltline without causing traffic diversion. No major compliance problems have been detected and the public acceptance of ramp meters as a means to improve safety and travel has been found to be very high.

(The full report lists specific results for safety, travel speeds, trip reliability, volumes, trip diversions, ramp meter compliance, and public perception.)

The northwest off-ramp of U.S. 12 (Madison, WI "Beltline") at Old Sauk Road, showing a former one-lane ramp has been improved to three lanes.

U.S. 12 (Madison Beltline) at Old Sauk Road - Rather than rebuild part or all of a 70's style traditional diamond interchange, only the two most congested ramps (diagonally opposite of each other) were addressed.

Bottleneck Project: The northwest quadrant exit lane (picture attached showing double right-turn lanes) and the diagonally opposite southeast quadrant exit lane (which was improved with double left-turn lanes) of this traditional style diamond interchange were each widened from one lane to three lanes to accommodate a recent boom in residential and commercial growth in the last decade or so. Rather than undertake a more-costly full redesign of the interchange to a partial- or full cloverleaf, the decision to only improve the deficient ramps saved money here. Some minor widening on Old Sauk Road was also undertaken to install exclusive turn lanes associated with the return movements.