SAN DIEGO I-15 Caltrans designs 32km of

SAN DIEGO I-15

Caltrans designs 32km of “managed” 3-lanes

Caltrans is designing a major expansion of the HOT lanes along I-15, the busy (250k veh/day) road slightly east of north out of San Diego. The proposal is to widen the existing 12km from 2-lanes to 3-lanes and to extend a 3-lane “managed lane” facility another 20km northward, in effect increasing 4-fold the pavement devoted to some mix of tolling and high occupancy. And they plan to install a moveable barrier the length of the facility so it can be managed directionally 3/0, 2/1, 1/2 or 0/3.

The existing 2-lane reversible HOT lane facility — the site of an AHS demonstration and now of dynamic priing — is 24 lane-km but the extended 3-lane facility would be 96 lane-km. With the moveable barrier running the full length there would be the ability to run a HOT lane in reverse commute for all or some of the rush hour. In time of a major sporting event, or an incident on the main lanes, the whole 3-lanes could be given over to one direction.

Conceptual design for the corridor is the work of the Advance Planning office of District 11 of Caltrans based in San Diego. Robert Robinson the project engineer in charge told TRnl that the managed 3-lane facility seems the most promising way of enhancing capacity in the I-15 corridor and that the idea will be incorporated in a major investment study beginning shortly. A Project Study Report laying out the “Managed 3-Lane” proposal will be completed by May.

Robinson says the existing I-15 HOT lane is not nearly long enough (12km) and needs greater capacity. His study will divide the facility into three sections:

• southern segment of 12km where the existing 2-lanes will be widened to 3-lanes and an extra transfer area (with entry and exit slip lanes each side — see diagram) will be provided at Mira Mesa Blvd

• middle segment of 13km from CA-56 where the current facility ends north to Centre City Pkwy of completely new central Managed 3-Lane facility with five transfer areas, about 2.5km apart

• northern segment of 7km from Centre City Pkwy to the CA-78 interchange at Escondido

Robinson says preliminary analysis shows the I-15 corridor is unsuitable for rail transit. A central “managed 3-lane” will serve the corridor’s needs better than additions to the general lanes — though the project also provides the free lanes an extra auxiliary lane at a number of points where weaving hampers traffic flows.

Mostly 5/3/5: The plan would give the roadway a lane configuration 7/3/7 and 6/3/6 alongside the Miramar naval air station at its southern end before the artery splits to CA-163 and CA-52. Most of it would be 5/3/5.

The whole project is $200m to $300m, Robinson says. Some widening of the right-of-way and property acquisition would be needed, especially in the middle segment, but by and large the project can be built by going to retaining walls and putting roadway over what are now slopes. Caltrans generally reduces lane width from the old 12 foot standard (3.65m) to 11’ (3.35m) in rebuilds, and in wide roadways like this, can gain a useful amount of extra pavement. No new direct connectors (flyovers from the central facility over the unrestricted lanes) are involved in the managed 3-lane project, though some existing direct connectors will have to be adapted to the wider ‘managed’ facility.

A fact sheet distributed on the proposal says that the aim of the managed lane would be to “maintain proper flow rates, sense problems, make adjustments and keep travelers informed of their choices.” Single occupant vehicles would be allowed into the lanes on payment of a variable toll but high occupant vehicles would have priority and if there were enough of these then SOVs might be excluded completely.

The goal would be use the moveable barrier to reconfigure the facility in 30 to 45 minutes. Current moveable barrier equipment operates at 6 to 10 km/hr to to change a 32km wall in 45 mins would take 3 or 4 machines operating at various positons along the wall. Robinson says he wants to push the Barrier Systems company to provide a faster machine. The equipment costs between $0.5m and $0.8m/km, so a movable wall of this length would be between $16m and $25m depending on the performance and numbers of transfer machines. Robinson wants 4 machines. The wall while enhancing the capacity of the project will probably constitute less than 10% of the overall cost.

Robinson says Caltrans District 11 is very comfortable about specifying the moveable barrier system because of some years of experience on the Coronado Bridge, where he says it works “very well.”

Assemblyman Jan Goldsmith who represents the area is an enthusiastic supporter of the project and says he is organizing support for any enabling legislation needed and for funds. (Contact Robert Robinson Caltrans-11, 619 688 3648)