IRIS
Intelligent Roadway Information System
Tolling
High-occupancy / toll (HOT) lanes can be operated through IRIS. Functions include logging vehicle transponder (tag) information, calculating tolls in real time, and displaying prices on DMS.
Customer accounts and billing are not supported; those features must be provided by an external system.
Tag Readers
Select View ➔ Lane Use ➔ Tag Readers menu item
A tag reader is a sensor for in-vehicle transponders (tags). They can be mounted over a tolled lane to record customer trips. These are typically located just downstream of a pricing DMS.
API Resources 🕵️
iris/api/tag_reader(primary)iris/api/tag_reader/{name}
| Access | Primary | Secondary |
|---|---|---|
| 👁️ View | name, location | geo_loc, settings |
| 💡 Manage | notes | toll_zone |
| 🔧 Configure | controller | pin |
Tag Read Events
When a tag is read, an event is logged in the tag_read_event database table.
The event includes the date and time, tag ID, toll zone and
tollway. This can be combined with the price message events to build a list
of trips for each tag ID. This information can be used to bill customers.
These records are purged automatically when older than the value of the
tag_read_event_purge_days system attribute.
Toll Zones
Select View ➔ Lane Use ➔ Toll Zones menu item
A toll zone is a segment of roadway between two stations. All HOT lane detectors between the starting station and ending station can be used to calculate the toll. Every 3 minutes, tolls are calculated using data from the most recent 6 minutes. Within a zone, each station has an associated toll, based on the highest density k recorded among HOT lane detectors downstream of that station.
p = α ⋅ k β
- α is the value of the
toll_density_alphasystem attribute, default 0.045 - β is the value of the
toll_density_betasystem attribute, default 1.10 - p is the calculated price
The toll price is then rounded to the nearest $0.25.
Pricing on DMS
The toll price can be displayed in DMS messages using DMS actions. A
[tz … ] action tag in the message pattern will be replaced with the
appropriate value. It has the following format:
[tz mode,{tz0},…{tzn} ]
Parameters
mode: Tolling mode:p: pricedo: openc: closed
tz0: First toll zone IDtz1-tzn: (Optional) additional toll zone IDs
If the tolling mode is priced, the tag will be replaced with the calculated
price, for example 2.75. It will be the sum of prices for all specified toll
zones. The values of the toll_min_price and toll_max_price
system attributes limit the calculated price.
For open and closed modes, the tag will be replaced with an empty string.
If required, a message such as OPEN or CLOSED may be appended after the tag.
Price Message Events
Price events are logged when a message is sent to a DMS, and again when the message is verified. The price event includes the date and time, DEPLOYED or VERIFIED status, DMS id, toll zone, highest density detector(s) and price.
The logged toll zone is the last zone specified in the tag. In priced mode, the displayed price is logged. For open or closed, a price of 0 is logged.
These records are purged automatically when older than the value of the
price_message_event_purge_days system attribute.