Customizing X-Plane Taxi Lines: Wed Editing Challenge

Rules

- Aircraft symbol position in the WED shows the exact position of the nose of the aircraft in the simulator.

- Aircraft symbol in the WED exactly oriented exactly with heading of the plane just taxied to parking

- Stand name has 2 words or less (like: Stand 01, Gate S15, Cargo_Ramp 22T)

- Hold short points connected with runway by a single segment. If this not possible - segment after hold short marked as taxiway, next and others - marked as runway.

- Taxilines what may be used as exit from runway only, marked as Oneway

- Excess segments (which can be dispensed without) removed

- Runway centerlines marked as Runway

Features

- force default dir for most file open dialogs to be current scenery pack

- make ToolTips in LibraryList more meaningful

- support jw docking to the 2nd door of the aircraft for XP 12.1.3+

Bug fix:

- minor accuracy improvement in map projection for very large objetcs

- fix duplicated exclusion zones at full scenery import

- WED-1507 fix exclusion polygons still green when locked

ATC taxi routes

• Taxi route segments cannot cross each other unless they are connected by a common node.
• The entire grid of taxi routes must be connected – there should be a continuous path from any one route to any other route.
• Every runway that is used in any flow needs to have a taxi route on it so aircraft can get from and to the runway.
• Segments are colour-coded when viewed in the ATC Taxi + Flow tab, to provide an immediate sense of the properties assigned to each segment.
• The most basic taxi route segment that can be defined is for taxiway on the pavement surrounding an airport.
• These segments are typically named to match the real-world route letters.
• They can also be defined as one-way routes if planes always use it in only one direction.
• Runway taxi route is defined by selecting the appropriate runway from the Runway drop-down menu.
• For all runway taxi routes, taxi route nodes must be inside of the runway’s bounds. Only a small overflow zone past the ends of the runways is allowed.
• Taxi routes must be parallel to and as close as possible to the runway’s centreline.
• The runway must be sufficiently covered by the taxi route. This includes displaced thresholds, but excludes blast pads.
• All runway taxi routes must be properly connected to the rest of the taxi route, as discussed in the Basics section.
• Hot zones are a location on an airport with a potential risk of collision or runway incursion, and where heightened attention by pilots and drivers is necessary.
• All taxi route segments inside the hold short lines of the real airport should be marked as hot zones.
• If the real-world airport is missing a hold short line on one side of the runway, a hot zone still needs to be marked approximately where the aircraft would have to stop in order to be out of the way of runway operations.
• When two runways cross, each one needs to have a hot zone marked near the crossing point of the other runway.
• An ILS critical zone is a designated area of an airport that all physical obstructions must remain clear of when one or more Instrument Landing Systems are in use, to protect against signal interference or attenuation that may lead to navigation errors, or accident.
• Each taxi route segment has a size letter, which restricts the use of that segment by aircraft larger than the specified size.
• A similar “stuck forever” situation can occur if ramp start positions that can be used by AI are on or close to taxi routes.
• WED 1.5 (and greater) now has more validations to ensure airport ATC taxi routes are accurate and sensible.
• Avoid “micromanaging” taxi routes. ATC and Ground Vehicle routes are intended to get traffic close enough to their destination that the built-in logic can taxi the vehicles to their final destination as needed.
• Avoid connecting taxi routes directly to ramp starts so that the aircraft has room to manoeuvre between the taxi network and the ramp start for the best, most realistic results.
• Use the fewest segments possible to specify only the desired & safe taxi routes. The taxi route is determined without checking for obstructions along the entire route–only the very next segment of the route is checked ahead of time, and the aircraft will not reroute if it becomes stuck.

Taxi route obstructions

Taxi routes are used by X-Plane ATC to provide navigation guidance around the airport. When creating taxi routes, it is important to be aware of potential obstructions that could cause issues for aircraft. Here are some tips to avoid taxi route obstructions:

• Avoid placing taxi routes directly connected to ramp starts, as this can cause issues with AI traffic. Instead, leave some space between the taxi route and the ramp start.
• Ensure that taxi routes do not cross each other unless they are connected by a common node. WED will automatically insert a node at the intersection to prevent this.
• The entire grid of taxi routes must be connected, forming a continuous path from any one route to another. Do not create disjointed movement areas, even if they exist in the real world.
• Every runway that is used in any flow needs to have a taxi route on it so that aircraft can get to and from the runway.
• Avoid "micromanaging" taxi routes. Specify only the preferred routes, as X-Plane cannot distinguish between plausible and rarely used routes.
• Use the fewest segments possible to define the desired and safe taxi routes.
• Avoid connecting taxi routes directly to ramp starts to allow room for aircraft to manoeuvre.
• Ensure that taxi routes do not go through buildings or other objects. Use the "Truck Parking" and "Truck Destination" tools to place ground service vehicle parking locations and destinations.
• When creating taxi routes, consider the size of the aircraft that will be using them. Specify the "Size" property to restrict the use of the taxi route to aircraft of a certain size.
• Use the "Validate" function in WED to check for errors and issues with your taxi routes.

Taxi route segments

• Departure/arrival hot zones
• Runway taxi route segments
• Basic taxi route segments

Departure/arrival hot zones

Hot zones are a location on an airport with a potential risk of collision or runway incursion, and where heightened attention by pilots and drivers is necessary. They are usually a segment of the taxiway closest to the runway, or where runways overlap. They are colour-coded red or purple in the map pane.

Runway taxi route segments

A runway taxi route is defined by selecting the appropriate runway from the Runway drop-down menu. The Name, Departures, Arrivals, and ILS Precision Area fields will be all be set automatically by WED. Runway segments are normally colour-coded blue in the WED map pane, but may also be purple if portions of that runway are also hot zones for other runways.

Basic taxi route segments

The most basic taxi route segment that can be defined is for taxiway on the pavement surrounding an airport. Typically, these are drawn over the line markings that guide aircraft around the airport. They are a collection of nodes and segments which are colour-coded yellow in the map pane.

Taxi route validations

The ATC taxi routes are used by X-Plane ATC to provide navigation guidance around the airport. ATC does not use any information other than the taxi routes; it does not matter where concrete and asphalt actually are, only where the Taxi Routes are.

Basic taxi route segments

The most basic taxi route segment that can be defined is for taxiway on the pavement surrounding an airport. Typically these are drawn over the line markings that guide aircraft around the airport. They are a collection of nodes and segments which are color coded yellow in the map pane.

These segments are typically named to match the real world route letters. You can leave the name blank for very small connectors and routes along the gate line. They can also be defined as one-way routes if planes always use it in only one direction.

To make a new taxi route, select the taxi routes tool and set the name and other properties in the tool bar, then click in the map pane to place the taxi route segments. The taxi route tool does not support bezier curves, so use short segments to approximate curves.

If you cross an existing taxi route segment while creating a new taxi route, WED will automatically insert a node at the intersection.

Runway taxi route segments

A runway taxi route is defined by selecting the appropriate runway from the Runway drop-down menu. The Name, Departures, Arrivals, and ILS Precision Area fields will be all be set automatically by WED. Runway segments are normally color coded blue in the WED map pane, but may also be purple – if portions of that runway are also hot zones for other runways (see below for information on hot zones).

For all runway taxi routes:

Taxi route nodes must be inside of the runway’s bounds. Only a small overflow zone past the ends of the runways is allowed.

Taxi routes must be parallel to and as close as possible to the runway’s centerline.

The runway must be sufficiently covered by the taxi route. This includes displaced thresholds, but excludes blast pads.

All runway taxi routes must be properly connected to the rest of the taxi route, as discussed in the Basics section

The property “Size” of runway segments has no function at all in X-plane.

Hot zones

Hot zones are a location on an airport with a potential risk of collision or runway incursion, and where heightened attention by pilots and drivers is necessary. Usually a segment of the taxiway closest to the runway, or where runways overlap, hot zones are color coded red or purple (when crossing or on a runway) in the map pane.

All taxi route segments inside the hold short lines of the real airport should be marked as hot zones. The presence of the hot zone will cause the AI aircraft to correctly hold short at those hold short lines.

If the real world airport is missing a hold short line on one side of the runway (this is rare, but does sometimes happen) you still need to mark a hot zone approximately where the aircraft would have to stop in order to be out of the way of runway operations.

Runways need hot zones too. When two runways cross, each one needs to have a hot zone marked near the crossing point of the other runway. If there are real land-and-hold-short markings (LAHSO) lines on the runway, this is a good place to start the hot zone. The hot zones are used when a runway is inactive (and being used as a taxiway), and also to detect conflicts between a landed aircraft that is taxiing off the runway and crossing arrivals and departures.

ILS critical zones

An ILS critical zone is a designated area of an airport that all physical obstructions must remain clear of when one or more Instrument Landing Systems are in use, to protect against signal interference or attenuation that may lead to navigation errors, or accident. ILS critical zones are color coded orange in the WED map pane.

Taxi route sizes

Each taxi route segment has a size letter, which restricts the use of that segment by aircraft larger than the specified size. The sizes depend on only the aircraft’s wingspan in X-Plane and are identical to ICAO aircraft size classifications:

Size Wingspan Examples

B < 24m King Air C90

C < 36m B737, A320, MD-80

D < 52m B767, A310, MD-10

E < 65m B777, B747, A340

Although this is useful to prevent oversized aircraft visibly hitting their wings on nearby scenery objects, care must be taken to not specify small sizes for no valid reason. The maximum size of aircraft that may taxi or be present at a given airport is limited by the largest size taxi route size specified in any of the ramp starts at that airport, plus runway size restrictions. If there is no path from any ramp start to the active runway wide enough to accommodate that aircraft, the ATC system may come to a full halt.

Taxi route obstructions

A similar “stuck forever” situation can occur if ramp start positions that can be used by AI (of type Tiedown or Gate) are on or close to taxi routes. ATC route planning will not check for such obstructions ahead of time, and if the shortest route to the runway happens to go along a route obstructed by a parked aircraft, AI traffic will stop indefinitely as it cannot re-route.

Validation checks

WED 1.5 (and greater) now has more validations to ensure airport ATC taxi routes are accurate and sensible.

If there are no ATC runway use rules specified, all runways are examined. Otherwise, only the runways mentioned in a runway use rule that also have at least one runway taxi route of the same name are checked during validation.

WED will display the boundaries where ATC taxi routes need hotzone after any failed validation in purple.

A good rule of thumb is to avoid “micromanaging” taxi routes. ATC and Ground Vehicle routes are intended to get traffic close enough to their destination that the built-in logic can taxi the vehicles to their final destination as needed. Specify only the preferred routes, as in general X-Plane can not tell non-plausible, obsolete or rarely used routes from the ones where you want aircraft to go.

Avoid connecting taxi routes directly to ramp starts so that the aircraft has room to maneuver between the taxi network and the ramp start for the best, most realistic results.

Use the fewest segments possible to specify only the desired & safe taxi routes. The taxi route is determined without checking for obstructions along the entire route–only the very next segment of the route is checked ahead of time, and the aircraft will not reroute if it becomes stuck.

Taxi route heuristics

Overview:

Benefits of Taxi Route Heuristics:

• Reduced Idle Time: Taxi route heuristics can help minimize the time taxis spend idling or waiting for passengers, reducing operational costs and fuel consumption.
• Improved Customer Satisfaction: By optimizing routes, heuristics can decrease passenger waiting times and provide faster, more direct journeys, enhancing the overall customer experience.
• Efficient Resource Utilization: Heuristics can optimize the utilization of taxi resources, ensuring that the right number of taxis are deployed to meet demand, reducing unnecessary trips and improving fleet management.
• Reduced Traffic Congestion: By optimizing routes, heuristics can help reduce traffic congestion, especially in urban areas, making roads more efficient and improving travel times for all vehicles.

Types of Taxi Route Heuristics:

There are various types of taxi route heuristics, each with its own advantages and considerations:

• Greedy Heuristic: This approach focuses on finding the shortest or fastest route from a taxi's current location to the passenger's pick-up point, without considering future requests. It is simple and effective for immediate trip optimization.
• Local Search Heuristic: This method starts with an initial solution and iteratively improves it by exploring neighboring solutions. It can find good solutions quickly but may get stuck in local optima.
• Simulated Annealing: This metaheuristic algorithm mimics the process of heating and cooling metals to find a global optimum. It explores various solutions and accepts worse solutions with a probability, allowing for a broader search space.
• Dynamic Programming: This technique breaks down a complex problem into smaller subproblems and solves each optimally. It is effective for problems with overlapping subproblems, but the computational complexity can be high.
• Machine Learning Algorithms: Advanced machine learning techniques, such as reinforcement learning or neural networks, can be used to optimize taxi routes based on historical data and real-time conditions.

Considerations for Effective Taxi Route Heuristics:

When designing taxi route heuristics, consider the following:

• Passenger Demand: Analyze passenger demand patterns to identify hotspots and high-demand areas. This helps in efficient taxi allocation and reduces idle time.
• Traffic Conditions: Incorporate real-time traffic data to optimize routes and avoid congestion, ensuring timely pickups and drop-offs.
• Taxi Availability: Consider the number of available taxis and their locations to ensure efficient utilization and reduce waiting times.
• Waiting Time and Extra Riding Time: Heuristics should aim to minimize waiting times for passengers and extra riding time due to ride-sharing, as these impact customer satisfaction.
• Operational Costs: Optimize routes to reduce mileage and fuel consumption, lowering operational costs for taxi companies.
• Customer Satisfaction: Heuristics should ultimately aim to enhance the customer experience by providing timely and efficient taxi services.

Case Study Example:

A case study in a suburban area of Nagaoka, Japan, optimized taxi allocation using heuristics. By analyzing taxi GPS data, they identified taxi demand hotspots and developed a mathematical model to minimize taxi idle time costs. They proposed three heuristic algorithms (greedy, simulated annealing, and dynamic greedy) and found that the dynamic greedy algorithm performed best, reducing idle time costs and CPU time. The optimized taxi allocation also led to an 81.84% reduction in CO2 emissions, showcasing the environmental benefits of efficient taxi route heuristics.

Frequently asked questions