Specification by Example¶

The best way to understand CDS is through evaluation of a series of increasingly complex examples. Below, we begin with single-sign examples, describing the policy or policies required to represent regulations on each sign. These single-sign examples do not include the catchall policy, which will be added when sign-specific policies are applied to a curb zone.

After evaluating individual signs, we consider examples of sign groups - representing a group of signs that are applicable to a specific zone. When evaluating sign groups, we will consider the complete set of policies applied to a zone with a particular set of parking signs and policies, including the catchall policy.

Single Sign Examples¶

30-Minute Parking¶

This sign represents a 30-minute parking limit, applied at all times. The limit is applied to all user classes and the sign is represented by a policy with the following rule:

Parking allowed, 30 minute max stay.

30 Minute Parking with a left arrow

Detailed Policy JSON

{
  "name": "Parking allowed, 30 minute max stay",
  "priority": 90,
  "rules": [
    {
      "activity": "parking",
      "max_stay": 30,
      "max_stay_unit": "minute"
    }
  ]
}

Street Cleaning Tuesday and Thursday¶

This sign prohibits parking on Tuesday and Thursday between 2 AM and 6 AM for street cleaning. It can be represented by a single policy with a single rule:

No Parking, Tue & Thur from 2 AM to 6 AM

Street Cleaning Tues-Thur, 2 AM to 6 AM

Detailed Policy JSON

{
  "name": "No Parking, Tue & Thur from 2 AM to 6 AM",
  "priority": 30,
  "rules": [
    {
      "activity": "no parking"
    }
  ],
  "time_spans": [
    {
      "days_of_week": ["tue", "thu"],
      "time_of_day_start": "02:00",
      "time_of_day_end": "06:00"
    }
  ]
}

Commercial Vehicle Parking¶

This sign prohibits parking except for commercial vehicles, which is limited to 30 minutes. This sign can be represented by one policy with a single rule:

Commercial vehicle loading, 30 minute limit, 7 AM to 7 PM, all days except Sunday.

Commercial Vehicle Parking, limit 30 minutes, 7 AM to 7 PM, except Sunday

Detailed Policy JSON

{
  "name": "Commercial vehicle loading, 30 minute limit, 7 AM to 7 PM, all days except Sunday",
  "priority": 40,
  "rules": [
    {
      "activity": "loading",
      "max_stay": 30,
      "max_stay_unit": "minute",
      "user_classes": ["commercial_vehicle"]
    },
    {
      "activity": "no loading",
      "user_classes_except": "commercial_vehicle"
    }
  ],
  "time_spans": [
    {
      "time_of_day_start": "07:00",
      "time_of_day_end": "19:00",
      "days_of_week": ["mon", "tue", "wed", "thu", "fri", "sat"]
    }
  ]
}

Explicit Prohibition

This policy explicitly prohibits loading for non-commercial vehicles during the designated time span to prevent fallthrough to the catchall unrestricted policy.

2-Hour Parking with Resident Exception¶

This next example addresses a 2-hour limit on parking, where area residents displaying a residential parking permit are not subject to the time limitation. This sign can be represented by one policy with a single rule:

2-hour limit except residents, 6 PM to 10 AM Mon-Fri

2-hour parking except for South Boston residents

Detailed Policy JSON

{
  "name": "2-hour limit except residents, 6 PM to 10 AM Mon-Fri",
  "priority": 40,
  "rules": [
    { "activity": "parking", "user_classes": ["resident_permit"] },
    {
      "activity": "parking",
      "max_stay": 2,
      "max_stay_unit": "hour",
      "user_classes_except": ["resident_permit"]
    }
  ],
  "time_spans": [
    {
      "time_of_day_start": "18:00",
      "time_of_day_end": "10:00",
      "days_of_week": ["mon", "tue", "wed", "thu", "fri"]
    }
  ]
}

Pick-up/Drop Off and Delivery¶

The sign below limits curb activities to pick-up/drop off and deliveries. For the Boston implementation of CDS, we are using the assertion that the activity loading allows loading and unloading of both people and goods. With this assumption, this sign can be represented by this simple policy with one rule:

Loading only, max stay 15 minutes, 8 AM to 10 PM except Sunday.

Pick-up/Drop off & Delivery Only Except Sunday, 8 AM to 10 PM

Detailed Policy JSON

{
  "name": "Loading only, max stay 15 minutes, 8 AM to 10 PM except Sunday",
  "priority": 80,
  "rules": [
    {
      "activity": "loading",
      "max_stay": 15,
      "max_stay_unit": "minute"
    },
    { "activity": "no parking" }
  ],
  "time_spans": [
    {
      "time_of_day_start": "08:00",
      "time_of_day_end": "22:00",
      "days_of_week": ["mon", "tue", "wed", "thu", "fri", "sat"]
    }
  ]
}

Explicit Prohibition

This policy example explicitly prohibits parking for all vehicles during the designated time span to prevent fallthrough to the catchall unrestricted policy.

Zone Examples¶

Each zone served by the CDS API will contain one or more policies that represent regulations on a particular curb segment. Examples of complete policy lists follow.

Snow Zone with Street Cleaning¶

This pair of signs, posted as a single physical sign, can represent the complete set of rules for a curb zone where parking is otherwise allowed. Because these two regulations are interpreted as two separate signs, this example uses two separate policies, plus the unrestricted catchall. The policy set for this sign is as follows, listed with the most important policy first:

No parking during snow emergencies.
No parking on Tuesdays from 12:01 AM to 7 AM.
Unrestricted parking.

No Parking, snow emergency or street cleaning

Detailed Policy JSON

```json [ { "name": "No parking during snow emergencies", "priority": 30, "rules": [{ "activity": "no parking" }], "time_spans": [ { "time_of_day_start": "00:00", "time_of_day_end": "00:00", "days_of_week": ["sun", "mon", "tue", "wed", "thu", "fri", "sat"], "designated_period": "snow emergency" } ] }, { "name": "No parking on Tuesdays from 12:01 AM to 7 AM", "priority": 35, "rules": [{ "activity": "no parking" }], "time_spans": [ { "time_of_day_start": "00:01", "time_of_day_end": "07:00", "days_of_week": ["tue"] } ] }, { "name": "Unrestricted parking", "priority": 99, "rules": [{ "activity": "parking" }], "time_spans": [ { "time_of_day_start": "00:00", "time_of_day_end": "00:00", "days_of_week": ["sun", "mon", "tue", "wed", "thu", "fri", "sat"] } ] } ]

```

Metered Parking, with snow zone and street cleaning¶

In many cases, snow zone and street cleaning signs are paired with other regulations such as 2-hour metered parking. The policy combination would be represented by the following policies:

No parking during snow emergencies.
No parking on Tuesdays from 12:01 AM to 7 AM.
2-hour Parking, 8 AM to 8 PM Except Sunday.
Unrestricted parking.

No Parking, snow emergency or street cleaning 2-hour metered marking

Detailed Policy JSON

[
  {
    "name": "No parking during snow emergencies",
    "priority": 30,
    "rules": [{ "activity": "no parking" }],
    "time_spans": [
      {
        "time_of_day_start": "00:00",
        "time_of_day_end": "00:00",
        "days_of_week": ["sun", "mon", "tue", "wed", "thu", "fri", "sat"],
        "designated_period": "snow emergency"
      }
    ]
  },
  {
    "name": "No parking on Tuesdays from 12:01 AM to 7 AM",
    "priority": 35,
    "rules": [{ "activity": "no parking" }],
    "time_spans": [
      {
        "time_of_day_start": "00:01",
        "time_of_day_end": "07:00",
        "days_of_week": ["tue"]
      }
    ]
  },
  {
    "name": "2-hour Parking, 8 AM to 8 PM Except Sunday.",
    "priority": 80,
    "rules": [{ "activity": "parking", "rate": [{ "rate": 200, "rate_unit": "hour" }] }],
    "time_spans": [
      {
        "time_of_day_start": "08:00",
        "time_of_day_end": "20:00",
        "days_of_week": ["mon", "tue", "wed", "thu", "fri", "sat"]
      }
    ]
  },
  {
    "name": "Unrestricted parking",
    "priority": 99,
    "rules": [{ "activity": "parking" }],
    "time_spans": [
      {
        "time_of_day_start": "00:00",
        "time_of_day_end": "00:00",
        "days_of_week": ["sun", "mon", "tue", "wed", "thu", "fri", "sat"]
      }
    ]
  }
]

Resident Parking, with snow zone¶

This next example addresses a 2-hour limit on parking, where area residents displaying a residential parking permit are not subject to the time limitation. This example also includes a snow emergency parking restriction.

No parking during snow emergencies.
2-hour limit except residents, 6 PM to 10 PM Mon-Sat
Unrestricted parking

Snow emergency with 2-hour Chinatown resident restriction from 6 PM to 10 PM

Detailed Policy JSON

[
  {
    "name": "No parking during snow emergencies",
    "priority": 30,
    "rules": [{ "activity": "no parking" }],
    "time_spans": [
      {
        "time_of_day_start": "00:00",
        "time_of_day_end": "00:00",
        "days_of_week": ["sun", "mon", "tue", "wed", "thu", "fri", "sat"],
        "designated_period": "snow emergency"
      }
    ]
  },
  {
    "name": "2-hour limit except residents, 6 PM to 10 PM Mon-Sat",
    "priority": 40,
    "rules": [
      { "activity": "parking", "user_classes": ["resident_permit"] },
      {
        "activity": "parking",
        "max_stay": 2,
        "max_stay_unit": "hour",
        "user_classes_except": ["resident_permit"]
      }
    ],
    "time_spans": [
      {
        "time_of_day_start": "18:00",
        "time_of_day_end": "22:00",
        "days_of_week": ["mon", "tue", "wed", "thu", "fri", "sat"]
      }
    ]
  },
  {
    "name": "Unrestricted parking",
    "priority": 99,
    "rules": [{ "activity": "parking" }],
    "time_spans": [
      {
        "time_of_day_start": "00:00",
        "time_of_day_end": "00:00",
        "days_of_week": ["sun", "mon", "tue", "wed", "thu", "fri", "sat"]
      }
    ]
  }
]

Loading Zone and No Stopping¶

This pair of signs designates a loading zone for the majority of the day, with no stopping allowed for 2 hours after the loading period ends. Unrestricted parking is allowed out of the designated times. It can be represented by the policies below.

No stopping for any vehicles from 4 PM to 6 PM, except Saturday and Sunday.
Loading only for all vehicles from 7 AM to 4 PM, 30 minute max.
Unrestricted parking.

Detailed Policy JSON

[
  {
    "name": "No stopping for any vehicles from 4 PM to 6 PM, except Saturday and Sunday",
    "priority": 30,
    "rules": [{ "activity": "no stopping" }],
    "time_spans": [
      {
        "time_of_day_start": "16:00",
        "time_of_day_end": "18:00",
        "days_of_week": ["mon", "tue", "wed", "thu", "fri"]
      }
    ]
  },
  {
    "name": "Loading only for all vehicles from 7 AM to 4 PM, 30 minute max",
    "priority": 80,
    "rules": [
      { "activity": "loading", "max_stay": 30, "max_stay_unit": "minute" },
      { "activity": "no parking"}
    ],
    "time_spans": [
      {
        "time_of_day_start": "07:00",
        "time_of_day_end": "16:00"
      }
    ]
  },
  {
    "name": "Unrestricted parking",
    "priority": 99,
    "rules": [{ "activity": "parking" }],
    "time_spans": [
      {
        "time_of_day_start": "00:00",
        "time_of_day_end": "00:00",
        "days_of_week": ["sun", "mon", "tue", "wed", "thu", "fri", "sat"]
      }
    ]
  }
]

Explicit Prohibition

This policy set example explicitly prohibits parking for all vehicles during the designated loading time span to prevent fallthrough to the catchall unrestricted policy.