OT: Slots on railways for timetable planning

Slightly OT, and one for those with operational knowledge of real railways:
Can anyone provide me with an explanation of how 'slots' work for planning
timetables?
TIA,
Ian J.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ian J. wrote:

Kindly supply an example of prose using the term in a t/t context. If it's short for "time slot", then it's a time during which a train can be on a piece of track (ie, the line between stations, the track along platform 1, etc.) It's obvious, I think, that two trains can't occupy the same piece of track during the same (time-)slot.
IMO, you will find that the graphic method of t/t planning works best.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Time slots as you describe them are what I'm after. I would like to know how they are used in planning timetables... Of particular concern to me is the way the length of a time slot is calculated, and how each time slot for one section of track connects up to time slots for ajoining sections of track.
Ian J.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ian J. wrote:

{(Length of track/average speed of train) + safety factor} --> {timeslot for that section of track}. Only one train can be on that section during any one timeslot.
Eg, assume section is 5km, the average train speed is 50km/h through that section, safety factor is 3 minutes, then the time slot is 15 minutes. That means you have to allow at least 15 minutes for any train running over that track section. Calculate the timeslots for every section of track on a given route, and that will be the minimum safe time over the route. You can calculate time slots for fast and slow trains, which is "merely" complication in planning the time table. That's why timetables are usually constructed graphically.
A "track section" is bounded by signals: the signalman (or the dispatcher at a central traffic control station) must know when each train enters and leaves a section, and whether or not it is on time.
Each track at a station is also track section: the minimum time slot is the time it takes to pick up and discharge passengers safely, usually reckoned at 1 to 3 minutes for timetabling purposes. On a single track line, trains have to cross at a station, so the minimum safe time is lengthened, since there has to be a safety margin to allow the trains to arrive from opposite directions, etc. Also, engine crew changes, servicing of dining cars, pickup and drop off of parcel freight etc can all affect the timeslot at a station. You can see that timeslots are not necessarily fixed, which is, er, another complication of time table planning.
Note that freight trains are also timetabled. They may be regular freights with a daily schedule, or they may be given ad hoc timings to fit them into the regular plan on that day.
For the graphic method, use a nice large sheet of 1/4" squared paper. (Tape several sheets together if necessary.) Calculate the distance between the stations, and write their names down the left hand side, separated by s suitably scaled distance. Eg, 10km (2 squares) to the half inch. Draw a horizontal line for each station. Mark hours from 00:00am to 24:00 (12 midnight) across the top at 1" to the hour, and draw vertical lines. A diagonal line drawn from one station to the next represents a train travelling between stations. The slope indicates both the direction (up and down) and the speed of the train.
If the lines of two trains intersect between stations where is no double track, then one or both lines will have to be adjusted so that the trains cross at a station. In practice, the premier trains are timetabled first, and the lesser ranked trains are fitted in between them.
I hope that's enough clues to get you going. Devising timetables can be a hobby in itself, so be warned... :-)
HTH
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Thanks for this, I will have to absorb it all before I can claim to understand it... :-)
Ian J.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Ian J. wrote: [...]

Here's a url for a research report on timetables for public use. About halfway down, there's an image of a graphic timetable, which should help you see what I meant. You will see sloping lines on a grid, not a very large image, but it should do.
http://www.communication.org.au/cria_publications/publication_id_91_439407953.html
Have fun!
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.