San Diego I-15 HOT Tolls to Vary 50c to $8.00 - changes possible each 6 minutes

January 7, 1998

San Diego I-15 HOT Tolls to Vary 50c to $8.00 - changes possible each 6 minutes

Originally published in issue 23 of Tollroads Newsletter, which came out in Jan 1998.


Subjects:Dynamic congestion pricing

Facilities:CA I-15


Locations:San Diego CA

Sources:Sarah Lawrence John Berg

San Diego I-15 HOT

Tolls to vary 50c to $8.00 — changes possible each 6 mins

The San Diego Association of Governments (SANDAG) toll buy-in program on the I-15 HOT lanes is now due to go to dynamic congestion pricing, apparently a world first, in March. The governing board recently gave staff the go-ahead to implement the congestion-variable tolls.

Consultants to SANDAG apparently had some last minute reservations about the dynamic price aspects project which will use computer algorithms and assumptions about the toll elasticity of demand to adjust toll rates dynamically to optimize traffic flows. Management however decided to “bite the bullet” and give it a minimum 2-month trial starting in March.

The idea of congestion pricing discussed in the economic literature for over 50 years has been made technically possible to implement with highway-speed electronic tolling, reliable highspeed vehicle count sensors, computers and variable message signs. The first steps in the direction of implementation have been “step pricing” in which different toll rates are charged in different time slots according to a pre-announced toll schedule — practiced by SANEF north of Paris, by 91-Express Calif and 407-ETR in Toronto.

But congestion pricing in its purest form yet is being implemented in the I-15 HOT project, where tolls will be varied in 50c increments between 50c and $8.00, depending on traffic levels. But it is not quite pure uncomplicated flow-driven congestion pricing. In response to focus group evidence that motorists prefer pre-trip start knowledge of toll rates, and concern about charges of “gouging” SANDAG will

(1) publish a stepped schedule of MAXIMUM toll rates in different half-hour time slots

(2) set a “normal” day maximum trip toll of $4/day and an abnormal day high of $8

(3) limit toll rate changes to a change every 6 mins

(4) make changes in 50c/trip increments avoiding large quick increases in toll rates, except on abormal days when $1 increases/6mins will come into play

The maximum toll schedule will be based on estimates of available lanes capacity after typical HOV volumes are allowed for, usage rates from the current monthly pass system, and comparisons with other toll facilities. As we go to press they have not yet been set.

Lawrence of SCAG explains: “The toll setting system will aggregate traffic volumes on the HOV lanes in six-minute increments. The decision whether to raise the toll, lower the toll, or keep it the same will be based on an average of two six-minute increments. The toll will increase or decrease by a fixed amount, normally 50c, to avoid large jumps in the toll. The maximum toll on a typical day is expected to be around $4.00.”

In cases of major incidents of the kind that happen two or three times a year, due say to a heavy truck accident, SANDAG will follow Caltrans policy of dropping tolls and HOV restrictions opening the HOT lanes to all traffic. The criterion for such an emergency free-for-all is two or more of the main lanes blocked for an hour or more.

Rain emergencies: Lawrence says that the situation they see as the most challenging is when there is very heavy traffic on the main lanes, due to a less severe accident or some rain (an extraordinary event in sunny San Diego!) that is not severe enough to warrant a big incident free-for-all but which is sufficiently severe to cause unusual congestion on the mixed lanes, and hence sharply increased demand for toll buy-in. In this scenario the toll system is planned to be switched to abnormal-day mode:

(1) toll increments will now be $1 instead of 50c

(2) the toll could go as high as $8.00 (60c/km).

“There will probably be claims of price gouging during these instances, but the alternative would be to close the HOV lanes to all of our paying customers,” says Lawrence.

“This system attempts to behave as dynamically as possible while still providing the driving public an idea about the toll levels. Commuters will know the maximum possible toll for each time interval and understand that they could receive a ‘discount’ if the traffic is lighter. Also, they will know that the toll will not normally increase or decrease more than a fixed amount, namely 50c in one toll adjustment.”

The I-15 team was concerned that a large toll rate change on a variable message sign might cause a motorist to suddenly change their mind and produce a dangerous swerve, in or out of the approach lanes. Lawrence says SANDAG is emphasizing the provisional nature of the meximum tolls schedule so it can make adjustments. The whole project is very experimental and Lawrence says:

“If after a few months of operations this system proves to be publicly unacceptable, then we could revert to a fixed, stepped toll schedule like 91-X. Only time will tell.”

Background: The I-15 HOT lanes are 13km of barriered central dual lanes inside a 2x4 and 2x5 unrestricted lane freeway just north of San Diego — a major tidal flow commuting and intercounty route. The 2 HOT lanes operate inbound morning rush hours and outbound evenings.

Under present arrangements solo drivers are buying-in to the special lanes by paying $90 for a monthly pass. At first this was a windshield sticker, but now it uses a California standard electronic toll transponder from Texas Instruments. Starting in March when the program will switch to a pay-per-trip or toll system for the solo drivers actual tolls will be indicated to motorists on the approaches to the HOT lanes on variable message signs.

SANDAG’s project will be systematically studied and reported on by teams of contract reviewers and monitors with federal highway funding. A lead role is being played by Janusz Supernak of San Diego State University. (Contact: Sarah Lawrence sla@SANDAG.COG.CA.US, Janusz Supernak 619 594 6378

“Much discussion preceded the SANDAG decision to go with a more

dynamic approach to pricing, with consultants arraying themselves on both ends of the spectrum, and I, for one, applaud SANDAG for trying to achieve something that more closely approximates true market conditions by time of day. The upper limit is probably a necessary concession to political reality, although it might in some circumstances limit the efficiency of the market response. Let's watch this one closely!”

— John Berg, Office of Policy, Federal Highway Admin posting on UMN cong pricing list-serv

Further Reading

Leave a comment:

Upcoming Events