Wednesday, April 2, 2014

More evidence that Carpool Lanes are NOT always "Underutilized" during off-peak hours

They may "look" empty with very few cars, but evidence shows that carpool and HOT lanes may be carrying thousands of people per hour during the off-peak hours.
The Transit Coalition has more evidence of why carpool lanes are not "underutilized" even though some may appear empty during off-peak hours. We took another field study down south, exploring and conducting a casual vehicle count of the I-15 Express Lanes through San Diego County, a robust multi-modal system that we would like to see extended north into the Inland Empire. The HOT lanes support free non-transponder carpooling--meaning that any high occupancy vehile with 2 or more passengers can get on for free and go without needing to pre-register ahead of time for a FasTrak transponder. The Express Lanes also have direct access ramps to/from adjacent transit hubs and park & ride lots; thus, they have bus transit infrastructure.

When we passed through during the early-afternoon off-peak hours, the general purpose lanes were at top speeds, but high in volume while the HOT lanes "looked" wide open. Because of that, many automatically imply that the carpool HOT lanes are "under-utilized" outside of rush hour. They are not, and here's what we found:

Counting the off-peak HOV's early in the afternoon

Early in the afternoon yesterday shortly after 2PM, we traveled northbound along the I-15 Express Lanes in San Diego County end-to-end and hand-counted the number of vehicles traveling southbound as we proceeded along. The southbound side of the freeway normally loads up during the morning rush hour, so it was clearly operating off-peak. Both the freeway and the HOT lanes were moving at fast speeds. The southbound side of the freeway lanes was a bit heavy, but moving at top speeds while the HOT lanes were wide-open as we counted approximately 300 total vehicles and 3 motorcycles in the express lanes during the 20-minute journey through the corridor. However, because the I-15 Express Lanes is a high occupancy vehicle facility, the question should not be how many cars are traveling through, but how many people.

We acknowledge that we do not have any special tools to weed out which cars were toll-paying solo drivers, but it's quite clear that very few solos will elect to buy their way into a carpool lane whenever the freeway lanes are congestion-free. Other than to travel in a wider-open set of lanes, why would one want to buy his/her way out of non-existent traffic congestion? With this reality, it was difficult to separate the HOV count from the toll-paying solos, but we'll do a very generous over-estimate that 10% of the traffic (or 30 of the cars counted) were toll-paying solo drivers.

We'll also subtract another big estimate of 30 cars for the few who own clean vehicles.

That leaves us with about 240 genuine HOV's counted in a twenty minute period. Multiply that by 3 to get an hourly average of 720 vehicles with at least two occupants in the carpool lanes during the 2PM off-peak hour on the southbound side.

A set of two freeway-speed HOT lanes have a vehicle capacity maximum of about 4,000-4,200 cars per hour, just like two general purpose lanes, so the lane will have a wide-open appearance outside of rush hours. That's why solo's are given the option to buy their way in at the market rate with dynamic FasTrak tolling, a fair alternative over the "open to all for free" option. To be fair, it is right and just to temporarily relax HOV restrictions and tolls whenever an incident occurs (e.g. sig-alerts, collisions, wildfires, maintenance, construction) to allow traffic to pass through freely for that short period, but during normal traffic conditions, tolling solos would prevent potential off-peak obstruction of the lanes. Also, some lighter Inland freeway corridors like SR-60 through Moreno Valley show that there are valid exceptions to this notion and that's exactly why HOV lane usage and enforcement policies need to be decided based on local traffic patterns, not from Sacramento politicians. That's why we don't support opening up the carpool lanes to all at the statewide level outside of rush hours. Back to San Diego County. With each of the 720 HOV's estimated having a least two persons inside, we have a bare minimum of 1,440 people for that hour traveling in the HOT lanes even though they look wide open and empty. That figure is definitely a lot higher, possibly breaking 2,000 people per hour.

Bring in MTS Route 20, the all-day local-plus-express bus route between south Escondido and downtown San Diego. While we didn't see the bus in the HOT lanes north of Rancho Bernardo during the field study, the bus runs every 30 minutes during the middle of the day. Suppose only 15 people were on board, a very low estimate. That's an extra 30 people per hour in the HOT lanes with only two vehicles. And wait until all-day rapid express BRT services are launched for the corridor. Let's not forget that since the HOT lanes support free-non transponder carpooling, private charter buses filled with people often pass through too. The lanes will carry even more people per hour even though that means few vehicles. We're talking thousands of people passing though per hour.

Does that sound "underutilized" during the off-peak hours? You make the call.

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