Second Life Railroad/SLRR standards

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==Description==
The Second Life Railroad uses a basic railway track for vehicles to run on. On this page you find the measurements and information associated with the railway track. The SLRR was originally designed to work under the prevailing conditions in SL; standards have not been published until recently. Many changes have occurred in Second Life since 2005, and there is work underway to establish formal standards to guide Resident rail content creation for use on the SLRR. This work was started on the 18th of August 2010 during a LDPW led Railway Brown Bag meeting with the Rail community. 
The SLRR is made up of specific prim sizes and names. The standards here are general measurements taken from in-world and put on the Second Life wiki pages. 
In the future a description of any open source scripts will also be made available here and some objects like the rail track components are made available at the "Mole Mart". 
===Open Access===
The SLRR has been operating since 2005, initially with Linden Lab's automated trains and later with trains built and operated by Second Life Residents. Already many Residents have personal trains they use on the SLRR. Second Life Residents have the right to operate trains on the SLRR, much as anyone can operate a car on the roads in SL. In addition, some Residents have used the SLRR track standards to build drivable railroads on their private lands.
Different train builders came up with a variety of train types with different propulsion methods. The SLRR Track standards have not changed much over the years and train builders found ever better ways to make their trains run on the SLRR. 
==Component information==
===Guidance===
Guidance is the actual way the vehicle "knows" where the track is and uses it to steer itself.
The existing system, Collision Guidance, involves a non-phantom (invisible) center rail, called Guide. The trains running on these tracks use this rail as a physical steering mechanism. A vehicle linear motor pushes the vehicle and collisions with the rail steers it.
Other vehicles use a sensor and target system to steer (Sensor Guidance), so collisions are unnecessary.
===Gauge===
Gauge is the width of the actual vehicle / track combination.
This is not very important, as it is for appearance only, but it would be good to have a standard that builders can use.
===Railbed===
Railbed is the actual track design.
There are presently:
*Flat - cheap for prims, does not look so good, good for sliding on.
*3-D phantom - costs more prims, looks good, good for sliding on.
*3-D non-phantom - costs more prims, looks good, creates a visible gap (the Havok Clearance of 0.1 meter) between sliding prims and rails.
===Switches===
Switches are used to help change the trains direction from one track to an other.
A separate page with switch standards has been created to fully explain how the work on the Linden SLRR tracks.
===Catenary Wires===
Catenary Wires are a cosmetic simulation of overhead electrical lines.
This is not very important, as it is for appearance only, but it would be good to have a standard that builders can use. Note that the SLRR doesn't currently have any catenary wire.
===Signals===
Signals are a signal lights that indicate specific states of the track.
* Semaphore signal are high standing light signals on movable arms. Currently (09-2010) they are only used to indicate a set track direction in conjunction with switches.
* Dwarf signals are low ground light signals. Currently (09-2010) they are only used to indicate a set track direction in conjunction with switches.
It has been made clear by that "running a red light" is not an offense according to the ToS. However a Physical driven train (and some Sensor driven trains) could derail at when the train crosses a red light near a switch for example.
===Control===
Control is the way the rail network as a whole works safely while sharing the rail resources among consists. 
Currently (09-2010) there is no such system in place.
Many people have suggested a control system on the public SLRR is not a good thing. Other say it is best to have a system that tells if there is on comming trafic on the track. And ohter residents suggest a full control system like on Real Life railroad tracks. On the Talk page you can voice your opinion about this subject.
==Standards==
===SLRR track standards===
(information based upon measurements taken from the original tracks made by Eric Linden.)
::*Gauge: 
The inside edge-to-edge distance between the rails. (center-to-center of the track prims is apporx. 2.15M)
 Size: 1.96M 
::*Railbed: 
To construct the Railbed (e.g. Gravel bed) you place a prim on a flat surface and set the measurements and attributes as given below. The length of the track is set in this example to 10.00 meter, but this can change according to your needs.
 prim size: prim rotation:
 x = 8.322 x = 0
 y = 10.00 * y = 0
 z = 0.686 z = 0
 
 prim attributes
 - Prim name: Atoll Railroad Section or SLRR Alternate Route **
 - Taper set to x 0.40
 - Taper set to y 0.00
 - NOT Phantom
 - Material: Glass
** The name Atoll Railroad Section is used for main section of track and SLRR Alternate Route is used for pass-tracks and spurs.
::*Track:
To construct the track (the actual rails themselves) you need to place 2 prims directly on top of the already constructed Railbed. And place them 2.15/2 (1.075m) left and right of the center of the Railbed. Do not forget to make the prims Phantom, so they don't interfere with the train wheels. The length of the track is set in this example to 10.00 meter, but this can change according to your needs.
 prim size: prim rotation:
 x = 0.173 x = 180
 y = 10.00 * y = 0
 z = 0.198 z = 0
 
 prim attributes
 - Taper set to x 0.50
 - Taper set to y 0.00
 - Phantom
::*Loading Gauge:
The clear width (from the centerline) and height (above the Guide) should be as follows:
 width = 4 meters; 4.5 meters on curves if longer cars are expected. 
 height = 8 meters for normal passenger and freight equipment; 9 meters for double-stack containers
4 meters width is a good standard for private routes, as it's the width of one "parcel block". The SLRR doesn't really support double-stack operation, though -- the numbers are given just as a standard for reference.<BR>
A nice Resident might wish to take a test run along the right-of-way and check for violations (Michael Linden) / Info shared (Stryker Jenkins).
::*Catenary Wires:
The SLRR doesn't currently feature any overhead electrical wire, but someday might. The wire would be 7 meters above the track (measured from the top of the rails). Other than that, no detailed specifications yet. The wire prim would probably be a phantom cylinder called "Catenary Wire", not linked to any other (phantom) cosmetic parts of a catenary system. Any overhead catenary construction that's within the loading gauge must be phantom.
::*Guidance:
To construct the Guidance place a prim on the Railbed and raise it so the bottom of this prim is at the same level as the top of the rails. Apply a full transparent texture to it. Next name the prim 'Guide' The length of the track is set in this example to 10.00 meter, but this can change according to your needs. Minimum distance between Guide prims should be about 5 meter. This also determines the 'sencor arc' in sensor driven trains.
 prim size: prim rotation:
 x = 10.00 * x = 0
 y = 0.5 y = 0
 z = 0.5 z = 0
 
 prim attributes
 - prim name: 'Guide', 'Alternate Guide'* or in special cases 'Tertiary Guide'*
 - NOT phantom (when more then 1 guidance prim is used with alternate names, as shown above, the alternate prims should be phantom) See switches.
 - note that the trackage in Bay City uses phantom Guides, to allow autos and trucks to more easily share the cargo areas.
 - Material: Glass
===SLRR track curves===
Curves in the SLRR tracks are made using shortened sections of the standard (straight) track.
There is currently no fixed data on how tight a curve can be (a.k.a. the radius). 
Experience has shown that a larger radius allows trains pass at any significant speed. Tighter curves tend to de-rail trains that use the center 'Guide' to steer. Separation between parallel tracks can be less with larger curve diameters.
To make curves use straight sections with a 
 length of 5 to 9 meters
and angle them no tighter then 
 15 degrees, but more typically 2-6 degrees
from each other, using the center of the guide as a pivot point.
===SLRR track Region crossings===
Border crossings are always tricky in SL. A much used method to improve this is to over lap the 'Guide' prim (2 in the same location more or less centered near the border). 
Then to Link 1 of those doubled up prims to the next 'Guide' prim on one one sim. And to link the other doubled up prims to the next 'Guide' prim on the other sim. Making sure that the doubled up prims is the 'child prim' and the prim completely over the sim is the 'root prim'.
 Comment: there have been reports of problems in following linked objects designated as "Guide" prims. 
 I'm not sure this system is the best solution. -- Michael Linden
===SLRR track switch===
Having the ability to switch from one track to the other is part of any rail network. This can be done in many different ways. It depends on the type of guidance used to make the train move along the tracks. But also on the type of trains that use the system.
On the following page a description is given about the LDPW switch.
LDPW is implementing a switch design that was presented to the rail community on August 18th 2010 during a Railway meeting.
===SLRR Buffer Stop===
At the end of a railway line we often find a Buffer. These are put there to prevent trains running of the track.<BR>
In SL this also exist in many way shapes and forms. Sensor driven trains can look for an object named
 Buffer Stop
Depending on the way the scripts in these trains work the sensor driven trains know when to stop and even to turn around when they encounter such an object.
An other method that is commonly used is to turn sensor driven trains around when they no longer "sence" the presence of more "Guide rails".
Most Physical trains rely on drivers to stop in time and turn around their train.
==Source==
The above information was collected by the Virtual Railway Consortium (VRC). 
Additions where provided by and others associated with other Railway related group. 
Linden Lab is currently the "operator" of the SLRR track. The VRC collected existing data for these wiki pages but did not set any standards. They evolved over time as Linden Lab 
employees constructed the Second Life Railroad.
==References==
Here is a list of Related resources. You can find more information about the SLRR and other Rail related articles on these wiki pages and external websites.
Wiki pages:
* Second_Life_Railroad (main page)
* SLRR History
* SLRR Standards
* SLRR Switch
* Linden Department of Public Works
* Linden_Vehicle_Tutorial
* Virtual_Railway_Consortium Group wiki page
* Virtual_Railway_Consortium/SLRR_History SLRR History main page compiled by the VRC 
* Virtual_Railway_Consortium/SLRR_Stations SLRR and Resident station along the SLRR
External information:
* Wikipedia: Rail gauge
* Physics related LSL on LSLwiki.net
* Vehicle related LSL on LSLwiki.net
* Virtual Railway Consortium
Category:SL_Railroad