HELP

Click the camera above to open a current snapshot of the Muni Subway in its own window. Then periodically update that snapshot window by clicking "Update Snapshot" at the bottom of it, or press F5. This large window can be closed at any time.

"SNAPSHOT" HELP

This website was created as a tool for Muni's operating and maintenance staff to remotely monitor the performance of the Muni Metro subway, as an aid in assessing and correcting problems.  Although not originally intended for the public, once the URL became known, Muni decided to continue to allow public access to the site.  To answer an increasing number of questions about the subway snapshot, the Image Explanation below has been created to help the public understand the symbols found in the snapshot.

In addition, answers to frequently-asked questions can be found further down this page, in the Image FAQ.

IMAGE EXPLANATION

The "snapshot" image represents the Muni Metro Subway.  It is electronically captured from the screen of one of the Train Control computers that is used to control the trains in the subway.  It is done in this very indirect way because the Train Control computers have no connection to the Internet -- nor to any other computers -- for reasons of safety and security.

THE TRACKS

The tracks that the trains travel on are represented by two light blue lines going from West Portal Station on the left to the Ferry Portal entrance (east of Embarcadero Station) on the right. The lower line is the Inbound track and the upper is the Outbound. The diagonal segments of light blue track rising above the horizontal track in the middle of the image are where N and J trains enter and leave the subway at Church and Duboce Streets. The tracks to the right of Embarcadero Station are used to turn trains around and to route trains into or out of the subway from the Embarcadero. 

THE STATIONS

Each station has two "platforms," shown as small, dark-blue squares. You can find them either between the two tracks (making up one "center platform") or outside the two tracks (making up two "side platforms"). Each platform is identified by a three letter abbreviation outside the track. See the table below. Tip: the third letter, R or L, in the abbreviation tells you if the platform is an Inbound (Right) or Outbound (Left) platform.

THE TRAINS

Trains are represented by small white squares.  A train's line (J, K, L, M, or N ) is shown by the letter that moves with the train. These letters are shown directly above or below the train, depending on which track section the train is occupying. Multiple-car trains have multiple letters such as JJ or KL.  The number of cars in a multiple-car train is also indicated by the number in the center of the train square.  A dot in the middle of the train square indicates that the doors of the train are open to let passengers on and off.  The train squares also change colors to indicate different events. The important colors to know are:

FREQUENTLY ASKED QUESTIONS

Why can’t I see any T trains in the snapshot?

The new T trains have not yet been given their own “T” labels in the Snapshot, so for now they are displayed as "K" in the inbound direction. Thus, all inbound "K" trains are actually T trains. It will be some time before the inbound T trains are labeled with a "T” because of the need for major modifications of the train control system under a new contract with the train control system vendor.

Why isn't the subway image more passenger-friendly?

The subway image that you see on your monitor has been electronically captured from the screen of one of the computers Muni uses to control subway trains. The symbols and layout of this screen were designed to be used solely by expert Train Control operators, not to give information to the general public. For train information specifically designed for use by the public, please visit Muni's NextBus website.

Does this image show what is happening in the subway at the time I download it?

Yes. A new subway image from the Central Train Control operator's screen is captured every 5 seconds.  This means that the image is at most 5 seconds old (plus the time it takes for your computer to download it). Each time you click "Update Snapshot", the most recent subway image is downloaded to replace your current one. The white timestamp in the lower right corner tells you when the image you are viewing was captured.

Why is the line letter (J, K, L, M, or N) of some trains black, while other trains are light-colored?

Trains whose letters are black are being controlled (i.e. "driven") by the central Train Control computer.  Trains whose letters are white or yellow are being driven by the train operator. For various operational reasons, both types of trains are often seen in the subway at the same time.

What does a dot (instead of a number) in a train square mean?

A dot means the train's doors are open.

Why are some track sections red instead of the normal light blue?

Tracks are shown in red when they have been "closed" by a Central Control Operator (CCO) or the Train Control system.  Computer-controlled trains cannot move in a closed track section.  The short track sections that are seen above and below the main track between Castro and Forest Hill stations are red because they are kept “closed” during normal operation. Tracks may also be closed for short periods. A CCO might close tracks, for example, to allow personnel to work safely on the track.  In addition, the Train Control system will automatically close tracks if it detects an intrusion or cannot verify the safety of all vehicles in the track section.

There are small colored spots along the track in front of a train. What do they mean?

The little spots along the track show the route that the train will be taking as it moves down the track.

Can the size of the image be changed?

No. It is permanently 630 by 272 pixels and is based on the resolution of the Central Train Control operator's screen, which is permanently fixed at 640 by 480 pixels. The higher the user's screen resolution, the smaller the image will appear on it. It will not lose any sharpness, however.

Copyright © 2006 San Francisco Municipal Railway.