Warrants

A Warrant is a collection of information sufficient to run an automated train. It will set the turnouts for a specified route and drive the train over the route. When running, using block occupancy detection and signal configuration, it will make a best effort to control speed according to signal aspects and occupancy and other track conditions ahead. A JMRI Warrant is suggestive of what a warrant does on a prototype railroad, but there is no intention to replicate any particular railroad's mode of operation. It is simply the idea of giving an automated train trackage rights to move from point A to point B.

Warrants depend on having an accurate description of the layout in terms of OBlocks, Portals and OPaths. These elements are created by entering data into the Occupancy Block Tables or by using the graphical interface of the Circuit Builder. Initially neither of these subsystems are visible in Control Panel editor.

It is important that the scale of your layout is known so that the warrant can compute the distances required when encountering signals. Go the Warrants panel of Preferences to set the layout scale. There are other parameters related to warrants there, that you may wish to change later, but the defaults are generally sufficient without change. See Warrant Preferences for information about configuration.

How To Get Started

What is Circuit Builder

Circuit Builder is an interactive tool that creates OBlocks, Portals and Paths graphically. It is necessary to have a track diagram of your layout expressed with track icons (track segments and turnout icons) in a Control Panel Editor panel. OBlocks are created by clicking on the track icons. The Circuit Builder can convert the track segments and turnout icons of your layout into Indicator Track and Indicator Turnout icons. These icons display the status of the OBlock they represent by color, i.e. whether the track circuit of the OBlock is occupied or unoccupied, whether a warrant has allocated it or whether a train under warrant currently is proceeding over the circuit. Details are found at The Circuit Builder,

Compatibility With Layout Editor

OBlocks, Portals and Paths can be used with Layout Editor. Compatibility is achieved by using the same occupancy detection sensors for LayoutBlocks as for OBlocks. If there is no corresponding Control Panel layout diagram, Circuit Builder cannot be used. The Occupancy Block Tables will have to be used to define the OBlocks, Portals and Paths.

More About Getting Started

In order to create a Warrant you must first have created two or more OBlocks. These blocks don't have to be fully defined, but their existence indicates that you are interested in using Warrants, that is, you have a block to start a train and a block to stop it. When two or more OBlocks exist Control Panel Editor will change the items under the Warrants menu to be the following menu items. The Warrant menu items are: The editor also will display a Circuit Builder menu. Otherwise, this menu is not displayed. The circuit Builder menu contains menu items to create and edit OBlocks, Portals and OPaths and to position icons that represent them.

Warrants without Occupancy Detection

It is possible to create and run warrants without block detection. OBlocks can be defined and they do not necessarily have to have detection sensors. Such blocks are called "Dark Blocks". Dark blocks, Portals and the paths within the block can be defined for a layout diagram. A Warrant can be recorded and be able to be played back, including having its route set. However, be advised for such trains there is no protection for having it collide with other trains or throwing switches under other trains. It will proceed only according to the elapsed times and throttle settings that were recorded.

The Importance of Block Path Lengths

A Warrant detects a position of its train when it enters a block having occupancy detection. All other positional information must be calculated. For this, the speed of the train and the length of the path it is on must be known. Please see Parameters Needed for Ramping below if you intend to use NXWarrants and employ gradual changes of speed.

Creating a Warrant

There are three types of warrants;

In either case, first a route must be chosen on which to run the train. The Creating Routes section below describes how this is done.

Elements of a Warrant

A warrant consists of two parts; The route over which a train will run and the commands it will receive when running over the route. For a Warrant, you drive the train over the route you selected and the commands you used are recorded for playback later. For an NXWarrant, commands are generated automatically for the route you have selected.

Creating Routes

A warrant route is a series of block paths linked together so a train may travel over it. A warrant route is created by first choosing an origin block, a starting path and a portal to exit the originating block. Then, a destination block is chosen and a path on which to end the route. Optionally, you may also chose a Via block, that is, a block that route must include and a Avoid block, that is, a block the the route must not include. Blocks are chosen by typing in the block name or dragging it from a displayed OBlock table. Blocks can also be chosen by clicking on track icons that represent these OBlocks. To use this feature your panel must have your layout depicted by Indicator Track Icons placed there by Circuit builder or by you manually. Successive clicks cycle the choices through the four block fields.

A computer algorithm determines all the intermediate blocks, portals and paths to make the route. If more than one route meets the criterion, you are presented with a list to review and select the route you want. Note that the Portal and Paths need to be chosen for the route also. If no route is found, a dialog is offered where you can examine the routes that were attempted with the current Block, Portal and Path selections. Creating and Editing Warrants has more information about creating routes.

Scripting the Train Action

The second part of a Warrant are the throttle commands to control the train as it traverses the route. These commands are recorded automatically by running a train over the route in "Learn Mode" or are generated automatically as an "NXWarrant". The script commands contain the elapsed time between commands. Playback will duplicate this timing. However when a warrant is run with a different engine or a different consist, or even the same train depending whether the motor is hot or cold, this timing may not be replicated exactly. Because of this the command script is synchronized upon entering each detection OBlock. So, if the train is slow in reaching the next block, the commands for the next block will be delayed until the train enters the block. Conversely, if the train reaches the next block ahead of time, any remaining commands in the block just left will issued with no elapsed time so that the train can catch up to the script.

Warrant scripts are recorded or generated with a "Clear", aspect throughout the route even through blocks with restricted speeds. These speeds in the script are the "Normal" speeds. However, after creation when running, track conditions may not be "Clear", due to a signal's speed restriction, a block's speed restriction, occupancy by a rouge train or even intevention by you to halt the train. Warrants are able to deal with these restrictions and will modify their Normal" speeds as needed to comply with the restrictions. The section "Warrants and Speed Restrictions" below explains this relationship.

Recording Scripts

This is done by putting a screen throttle into Learn Mode that records all the throttle commands you make when driving the train over the route. This script can then be replayed to drive the train automatically. All possible throttle functions can be recorded and played back.

With LocoNet you may steal the address and manual LocoNet throttle. For other command systems, a WiFi throttle may take the same address as the screen throttle and be used to record a walk around script.

Generated Scripts

For NXWarrants the script is generated by the warrant itself. It ramps the train up to a specified speed and ramps it down at the destination. It obeys all the traffic occupancy and signals as do the recorded warrants. See About NXWarrants for how to run them.

Customizing the Script

A warrant script can be edited to modify the recorded commands. Additional non-throttle events can be added to the script such as triggering or responding to external sensors. Creating and Editing Warrants. has more information about creating and customizing scripts.

Warrants and Speed Restrictions

A train running under a warrant must be aware of track conditions ahead. Signals may indicate reduced speed or permission to return to normal speed. Blocks may impose yard limit speed restrictions. Rogue trains may show up unexpectedly in the route. In our imagination, we can presume their detection means our warrant "engineer" sees a fusse. For each of these cases the warrant must look ahead, detect the need for a speed change and schedule the right time to do it - all the while making the change smoothly and completing it in prototypical fashion.

Configuring Speed Restrictions

For a warrant to detect a signaled speed change the signal must be configured in the Occupancy Block Tables. The Signal Table there configures the entrance Portal to the OBlock that the signal protects. The warrant then uses the signal system configured for the signal to detect the aspect speed.

Likewise, block speeds are configured in the Occupancy Block Tables. A column in the OBlock Table allows you to choose an aspect speed that the warrant will enforce.

When a occupancy sensor is activated ahead of the train on its route, the warrant will take note of it and make any necessary speed change.

Finally, you can instruct the warrant to ramp down to a stop or issue an emergency stop. Also, you can ramp up from a stop and resume the former speed.

When a warrant ramps down a speed change due to a signal, block or rouge occupancy condition, That speed change remains in effect until the condition is removed. At that time the speed is ramped up to the previous "normal" speed. The precedence order is: rouge occupancy, signal aspect, block speed.

A Note About Ramps

When JMRI needs to intervene and enforce a speed change that was not recorded, several calculations must be made. Two pieces of information are vital. There are several options in providing this information and there are default values for all of the parameters. You may want to experiment with warrants using these default settings and defer reading the following sections until later.

Parameters Needed for Ramping

To compute how far to look ahead and the time when to modify speed the following must be known. The smoothness for slow down and speed up are done by stepping up and down with two "ramp" parameters; the throttle increment per step and the time interval of each step. These two parameters are paired to make a "stair step" pattern for changing speed. Generally, they are paired in that a small throttle increment should be done in a short time interval and a large increment in a longer time. When setting them, the time interval should be long enough for the speed increment to complete given the momentum you have programmed into your decoders. They are set in >Edit->Preferences->Warrants.

Getting Speed Profiles for Your Trains

Converting a throttle setting to achieve a given track speed is dependent on the engine and its decoder. The decoder's speed curve to deliver voltage to the motor, and the motor's rpm response under load with that voltage is rarely linear. Likewise, whether the motor is driving the train forward or reverse often results in different track speeds.

A Speed Profile can be made for an engine that will provide the necessary factors to set throttle settings that will result in more accurate track speeds. These profiles are maintained in the Roster and there is a tool that will create them at Roster->Speed Profiling. Alternatively, Speed Profile factors for a selected set of throttle settings for the motive power used in a warrant can be determined by using the NXWarrant Compute Throttle Factor checkbox.

NXWarrants have a feature whereby running the train over a block of known length will compute a speed profile throttle factor for the train. Frequently, calibrating a slow, medium and fast throttle setting for both forward and reverse will be sufficient. See About NXWarrants.

Aspect Speed Map and its Interpretation

Speeds are named in the aspects.xml files that signal masts use in the Signal Mast System. These speed names are also used in the Blocks tables. To control train speed, values must be assigned to these speed names. The Aspect Speed Map found at >Edit->Preferences->Warrants provides a value for each named speed. It is up to the user to assign a value to the name and a meaning to the value. On the preferences warrant panel there are four radio buttons to assign meaning to the values entered into the Speed Map Table.

In defining the four choices, to help explain them we'll use a few examples and compare them as the warrants approach a signal whose entrance speed name is "Medium". In the examples, the throttle setting for "Normal" is the recorded throttle setting when approaching the signal.
Warrant#1 is recorded with Engine A and it achieves a scale speed of 60 mph (or 96 kmph) at a throttle setting of 0.8 (102 speed steps). This was the "Normal" speed recorded by the warrant approaching the signal.
We will also assume engines B and C use Warrant#1. Engine B only reaches a scale speed 50 mph at an 0.8 throttle setting and Engine C attains a scale speed 70 mph at an 0.8 throttle setting is also used in the warrant.
Warrant#2 is recorded with engine C and the "Normal" throttle setting approaching the signal was 0.68 which would be about 60 mph.
Warrant#3 is a slow freight recorded with engine C and the "Normal" throttle setting approaching the signal was 0.36, which would be about 31.5 mph.

We have the situation where the warrants are looking ahead to a signal showing an aspect of "Medium" speed. The prototype railroad using this signal defines medium speed as 30 mph. We will also assume we have set the Aspect speed name value to be the best guess we can make to duplicate prototypical speed at layout scale.

To sum up; if you are not fussy about being prototypical and always want to see speed change when signals are passed, use "Percent of Normal". If you have calibrated a sufficient Speed Profile for each of your engines you can use either of the last two speed interpretations which express throttle setting in terms of scale track speed.

The Signal Head Appearance Table

If signal heads are used on the layout, their appearances can be mapped to the speed names of signal masts in this table on the warrant preferences panel.

One use of this is to use virtual signal heads to dynamically influence the behavior of warrants. The appearance of these signals can be set either by panel icons or Logix. Since there are 8 possible signal head appearances additional speed names can be created so a unique speed can be made for each appearance.

Editing the Speed Map Table

Rows can be added or deleted. The default speed map has the names "Fifty" and "Sixty". These names only appear in signal mast systems for UP-2008 and BNSF-1996, so they can safely be deleted if you do use these signal systems. You only need but must have all the speed names that appear in the signal system you have configured for your layout.

If you add a new speed name for a signal head appearance, then add a row for that name in the Signal Map Table.

Block speed Names

A speed name can be set for each block by selecting a name from the Speed Notch column of the OBlock Table. One use of this feature could be to enforce a yard limit speed. Unlike signal speed names, block speed names are bi-directional. To return a warrant's speed to normal when leaving a yard limit, the speed names of the OBlocks on either side of the yard block should set to "Normal". Use care when combining this feature with signals to avoid providing conflicting speed change messages.

To unset an OBlock speed name choose the blank setting from the Speed Limit column. As with the absence of a signal, when there is no speed name the warrant continues at its current speed.

Using the Warrant List

The Warrant List menu item opens the Warrant Table. Each row is a warrant that has been created and saved or is a running NXWarrant. The Warrant Table reports the current status of each warrant in the list and can issue commands to Halt, Resume or Abort. Warrant routes can be allocated, i.e. reserved for that warrant, the turnouts for route can be set and when the warrant is run, its status is shown and controlled using the columns in the table. See The Warrant List for information about the table.

Tracking Trains

Any train running on the layout can be tracked. The layout must be represented with Indicator Track Icons to track trains. The fourth Warrants menu item opens the Tracker Table. Pressing the New Tracker button in this window opens a dialog to enter a train name and the OBlock it occupies. Pressing the done button creates a row in the Tracking Table. The row shows the train name and the block it currently occupies and the length of time it has occupied the block. As the train moves from block to block, this status is updated. The Indicator Track Icons can display the train name.
Note: The Edit Icon popup menu item opens a dialog for Indicator Track Icons have a Display Train Name when occupied checkbox to select to display text for train tracking or warrant running.
The window also has a Refresh Tracker Info button to poll the trackers listed in the Tracker table and a OBlock Pick List button to display a picklist.

The location of the train can be set by typing, by dragging block name from the picklist, or by clicking on a Indicator Track Icon in the panel.

Tracking can also be done for a train by dragging and dropping a Loco Icon onto the OBlock the train occupies. This is the most simple way of tracking in that both the names and location are done with a single drag and drop.

Using Warrants in Logix

Several of the operations that can be done from the Warrant List and Warrant Editing frame can be done with Logix Conditionals. You may design and implement a dispatcher's panel using the Warrant state variables and actions found in Logix.

Warrant State Variables

When a warrant has been allocated or is in effect, the following state variables can be tested in a Logix conditional.

Warrant Actions