Streets will be closed and Muni routes will be affected downtown virtually all day Saturday to clear the way for a mock terrorist attack.

Scores of local and federal agencies will simulate nuclear attacks beginning at 10 a.m. at 555 California St. and at 1 Post St.

Community events throughout The City and a preseason 49ers game will also affect roads and transit, according to the San Francisco Municipal Transportation Authority.

Saturday 7 a.m. to 11 p.m. downtown street closures

• - Montgomery Street from Sacramento Street to Market Street
• - Pine Street from Battery Street to Kearny Street
• - Post Street from Kearny Street to Montgomery Street
• - Leidesdorff Street from Pine Street to California Street
• - Intersections: Sansome and Pine, Leidesdorff and Pine, Montgomery and Pine, Post and Montgomery, Bush and Montgomery and Sutter and Montgomery

Saturday 7 a.m. to 11 p.m. downtown Muni disruptions

• - California cable car
• - 2-Clement
• - 3-Jackson
• - 10-Townsend

Other Saturday street closures and affected Muni routes

• - Stockton Street from Filbert to Union streets will close from 6 a.m. to 11 p.m. The 39-Coit Muni route will be affected. This is for a celebration of Italian culture with free entertainment planned by the San Francisco Italian Athletic Club.
• - Buchanan Street from Hayes Street, and Ivy Street from Laguna to Webster, will close from 9 a.m. to 7 p.m. This is for an all-day block party.

Sunday street closures

• - Beckett Street from Jackson Street to Pacific Avenue will close from 7 a.m. to 10 p.m. This is for a Ma-Tsu Temple Event.
• - Grove Street from Divisadero to Broderick streets from 8 a.m. to 3 p.m. This is for the Grove Street farmers market.

Sunday 49ers game

• - The San Francisco 49ers will host their first home preseason game Saturday starting at 6 p.m. at Candlestick Park. Delays are expected on all bridges and freeways leading into San Francisco before and after the game.
• - For service to and from the game, T-Third customers can transfer at the Gilman-Paul station to the 87S Candlestick Shuttle, which operates directly from the station to Candlestick and returns at the end of the game.
• - Muni Express routes are special event fare service with an adult fare of $7 roundtrip.

Pregame routes

• - 75X (Candlestick Express — from Balboa Park BART
• - 77X (formerly known as 47X) Candlestick Express — from California and Van Ness
• - 78X (formerly known as 28X) Candlestick Express — from California and Funston
• - 79X (formerly known as 9X) Candlestick Express — from Sutter and Sansome
• - 86S Candlestick Shuttle — from Bacon and San Bruno

Post-game routes

• - 75X Candlestick Express — to Balboa Park BART
• - 77X (formerly known as 47X) Candlestick Express — to Van Ness and North Point
• - 78X (formerly known as 28X) Candlestick Express — to California and Funston
• - 79X (formerly known as 9X) Candlestick Express — to Kearny and Sutter
• - 86S Candlestick Express — to Bacon and San Bruno

Source: San Francisco Municipal Transportation Authority