Mnpass Pricing and Its Benefits to Drivers
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MnPASS Pricing and Its Benefits to Drivers Chunying Xie Introduction Quantifying motorists’ values of $1.00 and continued to drop as the he MnPASS system allows solo time on the road is crucial to under- price rose. At $1.50, only 31% were drivers to travel in carpool lanes standing the policy implications of willing to pay the toll required to travel Tfor a fee. The system was imple- real-time pricing. To measure motorists’ the HOT lane. mented in 2005 when it was clear that value of time on the road, a data set that But our driver knows that the higher carpool lanes on I-394 were underuti- reflects how motorists make entry deci- toll amount is a signal of congestion lized. Drivers purchase a transponder sions on the road was necessary. The ahead and will start paying again as the that reports when they are using the data used contain de-identified MnPASS price gets to some intermediate point. In carpool lane—now called the High- data from October 2009. our 2009 data set, drivers sense conges- Occupancy Toll (HOT) lane. This article tion ahead at a price of $1.75 and 67% uses real data to determine the impact of Basic MnPASS Entry Decision became willing to pay the toll again. that system on traffic flows and to docu- Consider a morning commuter heading Eventually, the toll became too high and ment the benefits. The research finds to downtown Minneapolis from her drivers became more willing to stay in this real-time pricing system is working home in the western suburbs, some- the general-purpose lanes despite the well for both those in the HOT lane and where west of I-494. She is driving alone increased travel time. those in general-purpose lanes. but has a MnPASS transponder and can The goal of the MnPASS system is to choose to use the HOT lane if it makes What Is Driver Time Worth? reduce congestion, with an emphasis on sense to her. MnPASS posts the current Estimating subscribers’ value of time keeping those in the HOT lanes moving toll at her entrance to help make her on the road is a two-step process: at a minimum of 50 mph. Solo drivers decision. Once she enters the MnPASS (1) estimate the evolution of down- with transponders can choose to travel lane, she has locked in that toll all the stream congestion and prices based on free in the general-purpose lanes—or to way to downtown. current conditions using minute-level pay a fee, in the form of an electroni- Our driver will be trying to mini- traffic and pricing data, and (2) estimate cally collected toll, to travel in the HOT mize her total cost: a combination of subscribers’ value of time using the lane. toll price and travel time. When the entry model and the first-stage estimates MnDOT uses a real-time pricing price is low, she might opt to take the to match subscribers’ entry decisions on system that adjusts the prices every 3 HOT lane. As the price goes up, she is the road. minutes based on traffic flows. Higher less likely to pay the HOT lane toll. A To make these estimates, I took prices are charged when the system look at Table 1 showed this to be true advantage of the dual price postings senses congestion in the HOT lane. for drivers in the 2009 data set. When MnDOT places on its toll signs. I focus Total costs can be as high as $8 for a trip the toll was $0.75, 70% of them took on the experience of the eastbound from the western suburbs to downtown the HOT lane, but that percentage morning commuter. Figure 2 shows Minneapolis. Higher prices signal solo dropped to 60% when the toll rose to Interstate 394 in Minnesota, with a drivers about congestion ahead, forcing MnPASS toll lane at left shows the HOT them to decide between a faster trip in lane, and Figure 3 provides examples of the HOT lane and a no-cost but slower Table 1. Percent of MnPASS Subscribers the HOT prices presented to solo drivers trip in the general-purpose lanes. Who Choose HOT Lane at Western End who have the option of using the HOT The I-394 MnPASS system is shown of I-394 at Different Toll Prices (author lane. The top number shows the price to in Figure 1. It covers the full length of estimates based on real data from Highway 100, and the bottom number road, from I-494 in the west to I-94 in October 2009) shows the total price all the way to I-94 the east, and provides the major access (and downtown). That last segment of link to downtown for commuters in the Percent Entering I-394, the 3-mile line reversible section western suburbs. The system consists Price HOT lane of road, can be the most congested of of two segments. West of Highway 100, $0.75 70% the general-purpose lanes, so drivers will the HOT lane is separated from general- be watching for clues that might draw purpose lanes by double-painted lines $1.00 60% them toward the HOT lanes and an and marked with diamonds. Between easier ride. Highway 100 and downtown, a 3-mile- $1.25 59% The bottom number can signal long reversible segment is situated congestion on that final segment. $1.50 31% between the eastbound and westbound MnDOT raises the price on the HOT lanes, separated by concrete barriers. $1.75 67% lane as drivers ahead move to those For inbound motorists, there are four lanes to avoid congestion on the separate entrances to the diamond $2.00 63% general-purpose lanes. MnDOT does lanes and one entrance to the reversible this to discourage too many drivers $2.25 55% lanes. from moving to the HOT lane and 10 CURA REPORTER Figure 1. I-394 MnPASS Segments and Entrances MnDOT website I-394 15 12 Wayzata Blvd. I-394 MnPASS Express Lanes Central Ave. 101 101 Gleason Lake Rd. Carlson Pkwy. 12 494 Plymouth Rd. Ridgedale Dr. Hopkins Crossroads Shelard Pkwy. 169 General Mills Blvd. 394 Winnetka Ave. Louisiana Ave. Park Place / Xenia Ave. 1 00 Legend Wirth Pkwy. Toll rate sign Penn Ave. Tolling location MnPASS open access (single or double-dashed white lines) 394 MnPASS restricted access 94 94 (solid, double-white lines) WINTER 2018–19 11 Figure 2: Interstate 394 in Minnesota, with a MnPASS toll lane at left Wikimedia Commons Wikimedia Figure 3: Example of MnPASS Toll Rate Sign (eastbound, approaching US Highway 169) Top rate is the price to travel the HOT lane from here to MN Highway 100. Bottom rate is the total price from here to I-94 (and downtown). MnDOT website Eastbound dynamic pricing showing the cost to go to Highway 100 and then all the way to I-94 downtown. slowing speeds below 50 mph. The 4 minutes is 10% if the price at Loui- trade-offs as drivers make the decision last segment is accessed just before the siana is $0.50 but 32% if the price at about whether or not to enter the HOT intersection with Highway 100. I looked Louisiana is $0.75 and 53% if the price lane. at the price signaled earlier at Louisiana at Louisiana is $1.00. These numbers Using that information, my esti- Avenue for the final section of MnPASS helped me understand the probabilities mates show the average value of time to downtown. That price covers both facing drivers who have a choice to of MnPASS subscribers is $62 per hour, the last section “diamond” segment avoid congestion. with a standard deviation of $23 per of the HOT lane and the “reversible” The other issue those drivers hour. This is equivalent to an annual segment. consider in making their decisions is income of $120,624, which is similar to My first task was to estimate prob- price. The total HOT price shown at the annual income of many commuters abilities of downstream congestion and Louisiana Avenue from there to I-94 traveling on the highway. According to prices. The top part of Table 2 shows is a fairly good predictor of what the the 2007–2011 American Community the distribution of the general-purpose price will be for the Highway 100 to Survey, the mean household incomes lane speed on the Highway 100 to I-94 I-94 segment alone, but it’s not perfect. are $116,668 and $131,035 of two segment conditional on the HOT price Those prices help solo drivers with tran- neighborhoods at the first two entrances presented at Louisiana. Results show sponders estimate what their costs will of MnPASS. (Even lower-income the probability of observing a higher be for traveling the reversible segment. commuters will pay that price if time is travel time in the general-purpose lanes The bottom part of Table 2 shows that critical to them. Furthermore, the HOT increases with the price presented at the probability of encountering a higher lanes add comfort and safety not avail- Louisiana. For example, the probability price at the entrance to the reversible able in congested traffic.) of no congestion (travel time equal to segment increases with the price shown 3 minutes) is 83% if the price at Loui- at Louisiana Avenue, helping drivers Efficiency Benefits siana is $0.50 but decreases to 41% if decide whether to enter the HOT lane In this section, I address two policy the price at Louisiana is $0.75, and 15% at that point.