This section of Allston will be transformed during the course of the Allston Multimodal Project, which transportation officials say will take eight years to complete. Photo courtesy of MassDOT

State transportation officials suggested punting once again on selecting a preferred design for a massive infrastructure project in Allston stretching across multiple modes of transportation, this time until at least next year.

After targeting this fall to decide on an arrangement of highway lanes, rail lines and pedestrian paths in a densely packed section of Boston — and whether to repair, replace or outright remove an aging viaduct carrying the Massachusetts Turnpike — Transportation Secretary Stephanie Pollack on Thursday recommended waiting until the spring or summer of 2021 to make the call.

The postponement would grant officials more time to work through options on the table, she said in a presentation to the Department of Transportation board’s subcommittees.

Many members of the public and local leaders want the department to embrace an all “at-grade” option that would replace the viaduct with new highway lanes at the same level as rail tracks and the Charles River, but the administration is not ready to embrace it as the preferred option without doing more analysis of permitting, impacts on the river, and MBTA commuter rail operations.

The delay will allow for more conversations between stakeholders with the hope of finding consensus, plus allow for additional analysis on a finance plan, according to Pollack’s presentation.

It will also push construction out by “a year or more,” in the process raising the costs on a project already projected to surpass $1 billion.

Officials will also explore a new option to conduct smaller-scope, easier-to-achieve maintenance.

The process will, however, put a crimp in Harvard University’s expansion plans for the area currently covered by the Turnpike and its offramps. The school picked a development team for the first 900,000-square-foot phase of the project at the end of last year.