For nearly two decades, Stanford University's campus growth has hinged on a promise that development will not worsen traffic on its campus.

Now, as the university petitions Santa Clara County for permission to add more than 2 million square feet of academic space and more than 3,000 housing units on its campus by 2035, that promise is about to face its most serious challenge yet.

According to the newly released Draft Environmental Impact Report (DEIR) for Stanford's general-use permit application, the university's expansion will create "significant and unavoidable" traffic impacts along numerous road segments and intersections that are already heavily congested during peak hours. These include numerous intersections along Foothill Expressway; the Page Mill Road off ramp from southbound Interstate 280; and the intersection of Alma Street and Charleston Road.

In most cases, traffic conditions are already bad and are expected to get worse with or without the expansion. In a few cases, the Stanford expansion would tip an already busy intersection into a "levels of service" of E or F, connoting heavy congestion. At Alma and Charleston, the project-generated traffic would cause a degradation from D to E, according to the analysis.

Stanford's chief strategy for ensuring traffic doesn't get worse would be the continuation of its "no net commute trips" policy, which commits the university to not generating more traffic during peak commute hours. The policy, which made its debut in Stanford's 2000 general-use permit, requires Santa Clara County to count cars at cordons throughout the campus twice a year and impose penalties if Stanford fails. The agreement also allows Stanford to get credit for reducing car trips off campus and factoring those reductions into its "no net new commute" calculations.

To date, Stanford has largely held up its end of the bargain, thanks to transit incentives, bike programs, bus fleets and other programs that encourage students, faculty and staff not to drive solo to campus. Stanford had exceeded the commute threshold on only three occasions, in each case by a very small margin (a little more than 1 percent), according to county officials.

Now, Palo Alto officials and their counterparts in other jurisdictions are wondering whether adding more than 9,000 students, faculty members and staff to the campus over the next 17 years will make the goal impossible to meet.

Traffic isn't the only area in which Stanford's expansion will create "significant and unavoidable" impacts, according to the impact report. "Construction noise" and "cultural resources" are also identified as areas where the impacts are inevitable. But given the region's housing shortage — which necessitates commuting — and the already dire traffic conditions during commute hours, it is the area that is getting the most attention during the comment period for the DEIR, which is set to close on Dec. 4.

Santa Clara County Planning Director Kirk Girard said that the county has received plenty of comment so far about the "no new trips" policy, with many comments emphasizing that the county needs to establish that such an approach would effectively manage traffic, Girard told the City Council during a study session this week.

Stanford does offer other mechanisms for fighting congestion. Another strategy is having the university help fund transportation improvements at adversely affected intersections. The impact study lists projects that Stanford could help implement, even as it acknowledges the severe challenges for some of these projects.

For example, at Foothill Expressway, which will experience significant worsening traffic at Arastradero, Hillview and San Antonio roads, the proposed improvement is to create an overpass or underpass. Such a project would certainly face significant political and financial hurdles, even with Stanford's "fair share" contribution.

Other projects are smaller: reconfiguring lanes at the busy intersection of El Camino and Page Mill Road; adding a second westbound left-turn lane on Page Mill and Hanover Street; and creating a new right-turn lane on northbound Alma, near Charleston.

The report itself isn't overly optimistic about Stanford's ability to take care of its traffic impacts.

"It is uncertain whether it would be feasible to improve some of the affected intersections if the No Net New Commute Trips standard is not achieved, if there are not sufficient additional funds to complete the intersection impacts, or if there are not sufficient off-campus projects available to reduce peak-hour traffic," the report states.

Given the uncertainty, some local officials believe Stanford should go even further in funding transportation improvements. With public transit key to Stanford's congestion-management plan, Palo Alto Councilmen Adrian Fine and Greg Tanaka suggested that the university should contribute toward grade separations along the Caltrain corridor. With the number of trains set to increase with Caltrain's pending electrification project, grade separations become more imperative because of the traffic jams that will occur when crossing-guard gates are constantly closed, Tanaka said.

Palo Alto officials are also calling for the county to demand more analysis of commute patterns, including the number of cars on streets in non-peak hours; identification of Stanford's primary and secondary corridors; and an analysis of how Stanford commuters are avoiding the counts by parking on local streets in adjacent neighborhoods.

Earlier this year, Mayor Greg Scharff signed a letter from the council containing that request and indicating that traffic is one of the areas that most concerns the city.

"Members of the community appreciate the university's focus on reducing commute trips to/from campus by single-occupant vehicles during peak commute hours but are increasingly skeptical that the university's trip-reduction programs are living up to their promise," the letter states.

Council members offered additional concerns during Monday's discussion of the Stanford general-use permit. Vice Mayor Liz Kniss and Councilwoman Karen Holman both wondered how the university's expansion will affect parks and other recreational facilities. Councilmen Eric Filseth and Adrian Fine both talked about how expanding the number of Stanford students and faculty will affect the availability of housing.

Scharff noted Stanford still doesn't have a long-term plan for fire services. Palo Alto has been providing fire services to Stanford since 1976, though that partnership was strained in 2013, when Stanford announced its desire to terminate the agreement. The two sides have been negotiating since then and Scharff indicated that the dispute could end up in litigation.

"I don't see how we can certify the EIR without a long-term plan for fire service," Scharff said. "Stanford has not come up with a plan, other than us providing it on a very short-term basis, and the parties are quite far apart on that issue."

County officials will hold at least two more public hearings on the impact report before the document is certified. To date, the response from the general public has been mostly muted. On Oct. 12, only a handful residents attended a hearing on the document in the Lucie Stern Community Center auditorium, where they were outnumbered by Stanford and county officials. Only three residents spoke publicly about the EIR, none about traffic.

Supervisor Joe Simitian, who represents Palo Alto on the board, this week made a plea for the community to get more involved in the process and make their concerns heard.

"This is not the time for timidity," said Simitian, who was scheduled to host a public meeting on the impact report on Oct. 19 at Palo Alto City Hall. "If you believe the EIR needs to be robust, if you believe it needs more work, we'd rather hear it now than later in the process."

Concerned residents will have several more opportunities to comment on the EIR. The county plans to hold a public hearing on the document on Thursday, Nov. 30, from 7 to 9 p.m., at the Palo Alto Art Center. Residents can also submit written comments to David.rader@pln.sccgov.org or send them to David Rader, 70 W. Hedding St., San Jose, CA 95110.

"This is a major development over a long period of time in an area very sensitive to major developments," Girard said at the Oct. 12 meeting. "We have a very sophisticated regulatory program. We have very sophisticated decision makers, and the imput of the community will receive a lot of attention."