Time a junction with Webster's formula
WEBSTER-2PH- Define geometry and enter turning movement volumes
- HCM saturation flow methodology built in
- Get cycle length and an optimized timing plan
Beat the red. Time every junction with Fowle Flow.
Webster timing, 0.1-second microsimulation and a 48-slot lane closure scan, all on your iPhone. Get the answer on site, before the next cycle starts.
Download Fowle Flow- 5 phasing schemes ranked
- Metric and imperial
- On-device simulation
Every slow cycle you leave unchecked is delay your drivers pay for. Listing data checked November 2026.
Run 1 · Two-phase
Harvest Lane + Mill Road
Watch 10 cycle failures.
Delay19.7 s/vehFailures10 cycles
Pick your first run
Choose your quick-start kit before the light changes
Three ways to put Fowle Flow to work in your first session. Tap a kit, copy its reference tag for your project notes, then download.
Replay your plan in 0.1-second steps
Demo green window closes in00:24
RUN-0.1S-REPLAY- Watch at 1×, 4× or 14× speed
- Per-movement delay and cycle failures flagged
- Models lane choice, bay spillback and pedestrians
Scan 48 slots for the cheapest closure
SCAN-48-SLOTS- 24 hours checked in 30-minute intervals
- Lowest-delay start time and queue curves
- Alternating traffic control plan per interval
Reference tags are labels for your own project notes. They are not payment codes, and no deposit, discount or reward is attached. Fowle Flow is installed from the App Store listing, where current price and terms are shown.
Six tools that live in your pocket, not on a desktop
Stop waiting for a spreadsheet to open. Run the numbers where the traffic actually is.
Webster plus HCM
Enter junction geometry and turning volumes. Fowle Flow applies Webster's formula with HCM saturation flow and returns an optimized signal timing plan.
Scheme ranker
Five phasing schemes, including split phasing, protected lefts and leading left-turn arrows, are scored side by side so the best fit rises to the top.
Capacity readouts
See intersection delay, volume-to-capacity ratio, LOS grade and 95th-percentile queue. Bay overflow warnings flag turn pockets that will spill.
Microsimulation replay
Stochastic arrivals run on your device at 0.1-second resolution. Watch the animated replay and read where cycles fail.
Work zone planner
Scan a full day in 30-minute steps to find the lowest-delay lane closure window, with queue curves and a control plan for each interval.
Timing Card export
Save a Signal Timing Card image to your photo library with cycle length, LOS grade and a proportional phase diagram, ready for your report or slide deck.
Under the hood: how Fowle Flow crunches a junction
You start by sketching the junction: legs, lanes, approach speed, lost time and turning movement volumes. Fowle Flow feeds those inputs through Webster's formula and HCM saturation flow methodology, then builds a timing plan sized to the demand you entered.
Next the built-in scheme ranker compares five phasing schemes. Each one gets delay, volume-to-capacity, LOS grade and a 95th-percentile queue, plus bay overflow warnings. Recommendations come with plain-language explanations, so you know why a scheme won.
Then you test it. The simulation engine generates stochastic vehicle arrivals on the device in 0.1-second steps. It models lane selection, bay spillback, gap acceptance for permitted turns and pedestrian interactions. You get per-movement delay statistics and a list of failed cycles, and the Field Guide inside the app explains the methodology when you need it.
| App name | Fowle Flow |
|---|---|
| Version | 2.0 |
| Platform | iOS |
| Category | Productivity |
| Latest release notes | Faster screen loading |
| Units | Metric and imperial |
| Simulation resolution | 0.1-second time steps |
| Phasing schemes | 5 |
| Work zone scan | 24 hours in 30-minute intervals |
| Pedestrian speed presets | 3 |
| Export | Signal Timing Card image |
| User ratings | None recorded yet |
From first leg to final report: your workflow, step by step
Junctions and Timing
- Define each leg, such as a North leg with a receiving lane, and set approach speed.
- Adjust lost time with the plus and minus buttons, and use sliders for scale.
- Enter turning volumes, including right-turn legs, then read the optimized plan.
- Pick metric or imperial and one of three pedestrian walking speed presets.
Simulate
- Open a run and read the headline: delay in seconds per vehicle, vehicles served and cycle failures.
- Tap Watch replay to see the junction from above, with a timeline and signal phase strip.
- Scan the Tidiness Points list: timestamped peak queues, first cycle failures and queue clears.
Work Zones
- Create a project, for example a 2-lane road resurfacing job, and let the app scan the day.
- See the best start time, finish time and a Good badge when no queue forms.
- Read the Window Landscape histogram to see how total delay changes by start time.
- Compare a late-night window against a start in the evening peak before you commit crews.
Share
- Export a Signal Timing Card with cycle length, LOS grade and the phase diagram.
- Drop it into a report, presentation or site message straight from your photo library.
About the Developer
The publisher name is not shown in the app's screenshots, so check the App Store listing for the developer's name and the privacy details it declares. Fowle Flow 2.0 is a Productivity app for iOS. Its simulation engine runs on the device, and the latest update focuses on faster screen loading.
The next green won't wait. Download Fowle Flow.
iOS · Productivity · Version 2.0 · Check the App Store listing for the current price. Installs in moments on a normal connection.
Download Fowle FlowRequires an iPhone with iOS. The listing shows the age rating and any in-app purchases before you install.