A/B Street LTN tool user guide

By Dustin Carlino

Updated 11 September 2022

Notes

• This guide is a work-in-progress.
• (If you would like to help write this or record tutorial videos, please get in touch!)
• Email dabreegster@gmail.com if you get stuck
• Skip through sections of these slides based on what you need to do

Basic navigation

• Similar to Google Maps, click and drag to pan
• Touch pad, mouse scroll wheel, or bottom-right buttons to zoom
• The app doesn’t work on mobile / tablets (no touch controls)

Basic navigation

• Many buttons have key shortcuts, shown when you hover

Background knowledge

• This tool doesn’t teach you any background about LTNs or modal filters
• Refer to the Sustrans guide
• Some use cases for this tool could be:
• Your council has published an LTN scheme, and you want to understand how it’ll impact your driving trips
• Your council has published an LTN scheme, and you want to evaluate if it will have the intended effects, and possibly design your own proposals building on their work
• You’d like to design LTNs in your area and bring the idea to your council or a campaigning group

Your workflow

1. Open the city you’re interested in (you may need to import a new one)
2. Pick the area where you want to design an LTN (you may need to adjust an existing boundary)
3. Design the LTN by placing filters and changing one-way streets
4. See how specific driving routes may change
5. Upload the proposal and share with stakeholders

Repeat / refine the LTN

Picking an area

• Before you can modify filters, view shortcutting traffic, and see how space is split into traffic cells, you have to decide what the area is
• An area is surrounded by perimeter / boundary roads
• Usually these are “main” or “arterial” roads, designed to handle more vehicle traffic
• The boundary might also be a river, large forest, railroad, etc
• More vehicle traffic is acceptable / expected along the perimeter
• An LTN’s purpose is to reduce shortcut traffic through the middle of the area

Picking an area

• To start, just click the best match for the area you want

Picking an area

• By default, the map is divided into areas based on main roads
• This often works fine, but might be wrong for many reasons:
• Bridges / tunnels
• Rivers
• Road classification
• You can start with the closest area to what you want, then adjust the boundary

Adjusting area boundaries

Adjusting area boundaries

Adjusting area boundaries

• You can add / remove one block at a time
• A block is roughly the space in between some roads
• (It can get weird with tunnels, bridges, large parks in between roads, etc)
• Use the keyboard controls to “paint” quickly
• Or sketch the entire area you want freehand

Adjusting area boundaries

• You can’t introduce “holes” in the area
• Add the left block before the right

Adjusting area boundaries

• Sometimes it just breaks and you can’t sketch the area you want
• File an issue or contact dabreegster@gmail.com if you get stuck and need help

Once you have an area…

You can see:

• Traffic cells and entrances/exits to them
• A heatmap of predicted shortcutting
• Existing one-way streets and modal filters

You can edit:

• Modal filter placement and type
• One-way street direction

Traffic cells

• The coloured cells show where you can drive without exiting onto the perimeter road
• The blue, purple, yellow, etc cells are disconnected
• The arrows show entrances/exits to each cell

Shortcuts

• White roads have no shortcuts
• Intuitively, there’s no reason to drive here unless you’re going there
• Darker red roads have more shortcuts
• You can hover over a road and see a specific number
• But what does this mean? Click the shortcut tool to find out

Shortcuts

• After selecting the shortcut tool, click a road to focus on it

This shortcut exits the area here

This shortcut enters the area here

Browse through the 22 possible paths

Shortcuts

• A single path cutting through the area, instead of sticking to the perimeter roads
• The tool calculates all possible paths
• (Filtering out trivial examples that enter from one boundary road, then immediately exit a few blocks down)
• Every shortcut might not be realistic
• Some shortcuts might have much more traffic than others and be a bigger problem
• We rarely have real traffic count data over an entire area, so this is just an approximation

Modal filters

• The filters shown when you open a map already exist, according to OpenStreetMap data

Modal filters

• Click a road to add a filter, or remove a filter that’s already there
• Change the filter type using the toolbox
• There’s no difference between the filter types; they’re just for communication
• Bus gates (using camera enforcement) are recommended on roads with bus routes

Diagonal filters

• Click 4-way intersections to toggle through diagonal filters
• Only the red “do not enter” icon shows the direction of the diagonal

Consequences of placing filters

• Sometimes, just one filter creates a new cell. This is usually good – traffic can’t detour a different way through the area

Consequences of placing filters

• But sometimes, traffic might just detour around and take the next street
• Use the red heatmap to see the detour

Traffic will just detour and take the south road now

Water-tight schemes

• In this example, you need 2 filters to create a new cell and stop east-west shortcuts
• This scheme is “water-tight” – there’s no way traffic can “leak” through

Drawing filters quickly

• Sometimes you want to split a big cell somewhere, but there are a bunch of roads to click on
• Use the freehand tool and then just draw a line (think Fruit Ninja!)

Drawing filters quickly

• This will add a filter on every road your line crosses
• You’ll probably want to adjust the specifics later. This is just a quick tool to try things out

One-ways

• One-way streets have arrows
• You can change any street’s direction with the tool

One-ways

• Select the tool, then click any road repeatedly to toggle through the 3 options

Errors

• If you place too many filters and make it impossible to drive on some streets at all, the tool will draw a red cell and tell you to remove some filters
• This doesn’t yet work for one-way streets – the tool won’t stop you from doing something wrong there!

Planning a route

• How will new filters change a driving route?
• Click “Plan route” at the top, and be patient with loading first time

Planning a route

• Click to add waypoints for the start and end of your trip
• Trips can only start at buildings – you may have to zoom in sometimes!
• You can drag the waypoints around

Planning a route

• Often the fastest route sticks to main roads anyway, and new filters have no effect
• Play with the slow-down factor to simulate heavier traffic on main roads, which is when drivers may try to take a shortcut

Planning a route

• If the route will change due to the filters, then the before and after routes are shown, along with an estimate of the time for each
• You can also show the walking & cycling route, to understand that it’s still direct

Planning a route

• The routes shown and the time estimates are all just examples to visualize that a driving trip is still possible
• Some of the current limitations with the routing:
• The path might loop around to avoid a left or right turn in unrealistic ways
• Walking and cycling routes are not yet adjusted to prefer quieter streets through newly created LTNs
• There are some known bugs near private roads

Iterating on your design

• By default, every route you plan is saved. You can also rename it

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• Use this to create example “test cases” to see how your LTN proposal affects some representative trips

Sharing your proposal

• Click “Manage proposals” at the top
• Click “Share”

Sharing your proposal

• There are other options to save and load proposals, and compare multiple ideas at a time
• This part of the app is still under development; you’re likely to hit some bugs. We’re working on it!

Data privacy

• The app stores the schemes you save and the routes you plan to your browser’s local storage; it does not track or report anything remotely
• The only thing you ever upload is a proposal for new filters and adjusted area boundaries. This only happens when you click “Share” and then send somebody the address in your browser

Thanks!

• Email dabreegster@gmail.com with questions/feedback or file an issue on Github