Ramp Metering Deployment in Kansas City

In April, 2010, KC SCOUT, the joint Kansas and Missouri traffic management agency for the Kansas City region, deployed the first regional application of ramp metering on seven interchanges along a 5-mile corridor of the I-435 corridor. This project was implemented because the corridor often experienced congestion during the peak commute periods, largely caused by friction and incidents due to merging at on-ramp locations. Increasing capacity or adding lanes would be expensive and difficult given limited right of way.

KC SCOUT identified the following five objectives for the ramp metering system:

• Reduce rear end and side swipe accidents
• Maintain or reduce travel time along corridor even with greater traffic volume
• Avoid ramp meter back up onto arterial streets
• Limit motorist wait time at ramp to 1 minute or less
• Reduce incident clearance time

The activation of the system was supported by an intense public education campaign designed to educate drivers on the intended purpose of the system, how to safely navigate the newly implemented traffic control devices, and the enforcement activities that would accompany non-compliance. Several evaluations of the system were performed. In 2011 initial evaluation was performed by Kansas and Missouri Departments of Transportation 6-months following the activation of the meters, with a follow-up evaluation completed at the 12-month interval. Another evaluation study was performed in 2011-2012 using archived data to assess whether the initial impacts reported in the original year continue over time.

Methodology:
The data used for the analysis consisted of loop detector speed and volume data and accident and incident management data. The study focused on morning peak period (6am to 8am) and afternoon peak period (4pm to 6pm).
For the 2010-2011 initial evaluation, data was compiled data for a 24-month period (March 2008 to March 2010) prior to the implementation of the metering system and for a 12-month period (April 2010 to March 2011) following the activation.
For the 2011-2012 Long Term Impacts Evaluation, the data used was archived data from morning and afternoon peak hours for the all no-holiday weekdays following the activation of the system in April, 2010 through September, 2012.

Results:

Results of the initial 2011 evaluation include:

• Accidents were reduced by 64% along the I-435 ramp-metered corridor.
• Travel times decreased or stayed the same while increasing corridor throughput by as much as 20%.
• No ramp meter backed up on to city streets due to queue flushing policies.
• Motorist wait times were limited to less than 1 minute on all ramps.
• Incidents were cleared 16 to 22 minutes faster.

Results of the 2011-2012 Long Term Impacts Evaluation:

• The change in the average volume in the corridor for the longer-term evaluation period was observed to decrease by less than 4% in the morning peak and less than 3% in the afternoon peak compared with volumes observed in the initial evaluation. These results were not statistically significant and are within the range of normal fluctuation in traffic levels on the corridor for each peak period, suggesting that travelers have not significantly changed their use of this corridor during peak periods as compared to after the initial deployment of the ramp meters.
• Since the time of the initial evaluation, incident clearance times also proved stable overall. Incident clearance times during the morning peak period from April 2011 through March 2012 were on average 4 minutes shorter than in the extended term following the first year activation of the metering system.
• The analysis of the longer-term evaluation period from April 2011 through March 2012 concluded that peak period average speed, volume, and incident clearance time remain consistent in the period subsequent to the initial deployment and evaluation of the I-435 Corridor.

Additional Reference:
KC SCOUT (2011) Maximizing the Flow, Ramp Metering 2011 Evaluation Report. Kansas & Missouri DOT. http://www.kcscout.net/downloads/RampMetering/2011RampMeteringEvaluationReport.pdf