IRIS
Intelligent Roadway Information System
Ramp Meters
Select View ➔ Ramp Meters menu item
A ramp meter is a traffic signal at an on-ramp which controls the rate of vehicles entering a freeway. Typically, one vehicle is permitted to enter for each green indication displayed on the signal.
The following operations can be performed on a ramp meter:
- Activating and deactivating meter
- Adjusting meter release rate
- Querying meter status
- Querying green counts
- Synchronizing clock
- Configuring time-of-day operation
API Resources 🕵️
iris/api/ramp_meter(primary)iris/api/ramp_meter/{name}
| Access | Primary | Secondary |
|---|---|---|
| 👁️ View | name, location, fault | geo_loc |
| 👉 Operate | m_lock | rate |
| 💡 Manage | notes | storage, max_wait, algorithm, am_target, pm_target |
| 🔧 Configure | controller | pin, meter_type, beacon, preset |
Setup
| Field | Description |
|---|---|
| Notes | administrator notes, possibly including hashtags |
| Meter Type | number of metered lanes, etc. |
| Storage | distance from meter to queue detector |
| Max Wait | maximum allowed wait time (estimated) |
| Metering Algorithm | simple or density adaptive |
| AM Target | historical hourly AM target rate |
| PM Target | historical hourly PM target rate |
| Advance Warning Beacon | beacon activated automatically when active |
For basic time-of-day operation, the simple metering algorithm will run
the meter at a fixed release rate, equal to the target rate for the current
period (AM or PM).
The density adaptive algorithm requires a bit more configuration, since it
depends on the road topology. An entrance r_node must exist, with
matching roadway, road_dir, cross_street, cross_dir and cross_mod.
This r_node must have one green detector, plus optional queue,
passage, bypass and merge detectors.
There are special rules for meters on CD roads:
- The meter's
roadwaymust be the main road - The entrance r_node must be on the CD road
- The name of the CD road must be the same as the main roadway, but contain the word-token "CD"
Advance warning beacons are flashing lights on a static sign, e.g. "PREPARE TO STOP WHEN FLASHING". Typically, they are hard-wired to flash when the meter is operating, but they can be controlled by IRIS if that is not feasable. In that case, beacons will also flash if a merge detector on the entrance ramp has high occupancy (30%+).