"Over the past four months, we have repeatedly received such feedback, indicating that any improvement to mainline flow is achieved at the cost of increased delay to left turning and side street traffic."
That sentence comes from the SR68 Corridor Operations & Safety Evaluation, a review of the Highway 68 adaptive signal pilot presented to the Transportation Agency for Monterey County in June 2026. It describes something anyone driving between Monterey and Salinas this year may have noticed. Driving down the highway itself got a little faster. Turning onto it got slower. How your commute changed since spring depends on whether you spend it in the through lanes or waiting at a side-street light. That gap in the data is now the main case for rebuilding three intersections as roundabouts.
Nine Signals Running on One New Logic
In spring 2026, Caltrans switched the corridor's signals to an adaptive system run by Miovision. Caltrans' announcement gives the start date as Monday, May 4, 2026, while TAMC's May 27 board highlights say May 5. The consultant's May presentation explains the difference from the old timing plans. Coordinated signals "take time from side street to improve mainline traffic flow." Free operation splits time evenly. The adaptive system leans toward coordination at peak hours and toward free operation off-peak, and it adjusts for seasonal changes, special events and incidents. AI analytics read real-time traffic data within limits set with Caltrans, and the presentation calls it "not a 'set it and forget it' system."
The pilot covers every signalized intersection on the corridor, listed from west to east:
- Josselyn Canyon Road
- Olmstead Road
- SR-218 / Monterra Road
- Ragsdale Drive
- York Road
- Pasadera Drive / Boots Road
- Laureles Grade
- Corral de Tierra Road
- San Benancio Road
Caltrans treats Josselyn Canyon as the western end of the roughly nine-mile project. That puts the Monterra Road signal two lights in, close to the Monterey end. Drivers there are on both sides of the trade-off. Heading toward Salinas, they ride the improved mainline. Waiting at a red to get onto 68, they are the side-street traffic the evaluation describes.
What the Trade-Off Looks Like in Seconds
The June 24 evaluation presented to TAMC compared average delay per vehicle for the week of April 6–10, before the switch, with May 11–15, after it.
| Movement, peak period | April 6–10 delay per vehicle | May 11–15 delay per vehicle | Change |
|---|---|---|---|
| Westbound mainline, AM peak | 61.96 sec | 56.79 sec | 5.17 sec shorter |
| Eastbound mainline, PM peak | 60.38 sec | 54.32 sec | 6.06 sec shorter |
| Side streets, AM peak | 55.43 sec | 65.63 sec | 10.2 sec longer |
| Side streets, PM peak | 46.25 sec | 74.12 sec | 27.87 sec longer |
In the afternoon, side-street delay grew by more than four times what the mainline saved. Average side-street delay in the PM peak went from below the mainline figure to well above it. The same evaluation says longer waits for a green have "consistently triggered complaints" from left-turn and side-street drivers, and the slide that lists the delay numbers notes higher customer service request volumes.
The earlier May 27 presentation measured something else: end-to-end travel times from timed field runs. A westbound AM peak run took 43 minutes 48 seconds on March 17, 2026, and 38 minutes 8 seconds on May 12, 2026, a 13 percent improvement. A PM peak run between Josselyn and Reservation/River took 28 minutes 56 seconds before and 33 minutes 9 seconds after, which the slide labels a 14 percent increase. The presentation summed up its early findings in one line: "Adaptive operations improve mainline travel times & increase side street delay."
All of these are early numbers. The June evaluation says the accuracy of Miovision's data "remains under review due to erratic traffic counts observed during May and June." It also notes that operational complaints go to traffic operations engineers in San Luis Obispo, because the local maintenance crew does not yet support the new controllers. Caltrans' most recent status report, prepared September 11, says only that evaluation continues and that the team is answering customer service requests. It gives no newer figures.
How Side-Street Delay Became the Case for Roundabouts
Before the pilot, the roundabout proposal was compared against the old signals. Now the adaptive system is the comparison point. The public project page says adaptive operations serve as the baseline for the roundabout decision. At TAMC's August 26 meeting, Caltrans' Ryan Caldera reported that the Phase 1 roundabouts had been re-evaluated against conditions under adaptive signals. The analysis still found that they would improve safety and traffic operations and reduce the potential for serious-injury and fatal collisions by "simplifying intersection movements and lowering travel speeds."
Doug Bilse, TAMC's principal engineer, made the trade-off explicit in an interview with KSBW: "There's always been a trade-off between pushing more traffic along Highway 68 and holding up the traffic on the side." He told the station that preliminary data showed roundabouts would move "significantly more traffic than a traffic signal" and that "the side streets will get served a lot more efficiently."
A signal can give green time to the highway or to the side street, but not to both at once. The May presentation said as much: "Can't create time- so safety and queue instability remain with any signal operation." The roundabouts are proposed specifically to serve both at the same time.
Phase 1 covers San Benancio Road, Corral de Tierra Road and Laureles Grade. These are the three eastern intersections, about five to seven signals east of Monterra Road. The longer-term plan, Caltrans' adopted alternative, converts all nine signalized intersections to roundabouts and adds five wildlife culverts. The adaptive signals are the interim system for the whole corridor, including the Monterra Road signal, until the later phases are built.
The Pushback Uses the Same Numbers
Opposition along the corridor starts from the same data and draws a different conclusion. KSBW reported that Corral de Tierra residents who have long opposed the roundabout plan say the adaptive signals are already shortening queues, based on driving the road and watching Caltrans' live intersection cameras. One of them told the station that the modeling showed "only five minutes of relief in the PM peak commute and no relief on the AM commute," and set that against a $330 million cost. That cost figure is the opponent's own. Caltrans' September status report lists the Josselyn Canyon to San Benancio corridor project at $52.5 million. Another driver quoted by KSBW favored the AI approach, citing construction disruption and expense.
Farther west, Pasadera's homeowners association has formed a Highway 68 Committee. Its page specifically mentions long waits to turn left into Pasadera and directs feedback to County Supervisor Kate Daniels. That is the side-street delay from the June table, showing up at a specific gate.
At the August 26 meeting, a public speaker asked for more time to assess the adaptive signals. Board members discussed the volume of public complaints about current conditions. Chair Chaps Poduri asked staff to prepare and post answers to frequently asked questions on the TAMC website. The board then unanimously authorized staff to apply for Senate Bill 1 construction funding for Phase 1 from the California Transportation Commission.
The Calendar From Here
Caltrans' September 11 status report lists the corridor project in final design, with geotechnical work and right-of-way coordination ongoing. It projects construction from fall 2028 through spring 2031. The Caltrans project page still shows an older March 2028 to November 2030 window. Either way, the adaptive signals will run Highway 68 for at least two more years.
In the meantime, this week's work on the corridor has nothing to do with roundabouts:
- Overnight drainage work, Josselyn Canyon Road to Buena Vista Lane: alternating lane closures October 11–15, per TAMC's Cone Zone report.
- Toro Park ramps: full overnight on- and off-ramp closures October 11–16, from the same report.
- Utility work at Corral de Tierra and Laureles Grade: daytime traffic control with expected delays from 9 a.m. to 5 p.m. through October 26, according to the County of Monterey's road conditions page, last updated October 9. The County does not describe this as roundabout work.
If you have watched a light at the Monterra Road signal or Laureles Grade and wondered whose green time you were waiting on, Canning Properties Group follows corridor decisions like this one closely because they shape daily life across the neighborhoods we serve. Book an appointment and we can go over what the Highway 68 timeline means for your corner of the Peninsula.
