Attachment C.pdf

1.0 Travel Time and Speed Data Respondent Comment

1.1 Base Data Elements of Travel Time and Speed for All Roadways

1.1.1 Mean Travel Time

The Vendor shall report Travel Time to the nearest whole second (or equivalent such as decimal minutes)

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1.1.2 Mean Speed

Speed refers to the space-mean speed, NOT the instantaneous vehicle speed.

Speed, for the purpose of this RFP, refers to the observed time rate of traversal of a segment, defined as the length of the segment divided by the travel time. The

Vendor shall report Speed to a precision of the nearest 1 mph or greater

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1.1.3 Status Flag

The Vendor shall provide a status flag(s) per segment for each reported Travel

Time /Speed record to indicate the following:

Normal system operations with sufficient probe density to estimate travel times accurately.

Periods of low-traffic flow, travel time may need to be imputed from a combination of real-time data combined, historical data, and adjacent roadway segments.

Real-time probe data is not available, travel time is imputed based on historical data and/or adjacent roadway segments.

An example of existing status flag are scores of ‘30’, ‘20’ and ‘10’ to indicate whether data feed is based on real-time data (‘30’), combinations of real-time and historical data (‘20’) and assumed free flow (‘10’). This is only an example. Any status flag that reflect similar information is acceptable.

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1.1.4 Quality Indicator

The Vendor may provide a numerical score that reflects the confidence or anticipated error in the estimate of the mean travel time and speed. The intent is to

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provide a measure similar in concept to the standard error in the estimate of the mean. Vendor should provide explanation of the quality metric.

1.1.5 Roadway Coverage

Percentages of mileages covered for interstate, primary and secondary routes.

Vendors must use SCDOT “Statewide Highways” GIS file located here to determine these percentages. This file is publically accessible. Attribute

“ROUTE_TYPE” should be used to identify different route types: ‘I-’ for interstates, ‘US’ for US routes (primary), ‘SC’ for SC routes (primary), ‘S-’ for secondary routes and ‘R-, RS, CD, D’ for ramps.

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1.1.6 Sample size

The Vendor may provide the sample size (such as the number of base probes) for a given time frame (such as the number of observed probes in a 15-minute period).

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1.2 Travel Time and Speed Data Quality on Freeways and Arterials

1.2.1 Average Absolute Speed Error (AASE) for Freeways

Average Absolute Speed Error (AASE) is the average of the absolute value of the difference between the space mean speed reported from the data service and the space mean speed provided by validation procedures for a specified time period or polling interval.

AASE =

𝑇

∑ ∑|𝑆𝑉

𝑖𝑗

− 𝑆𝑅

𝑖𝑗 𝑚

𝐽=1 𝑛 𝑖=1

Where, 𝑆𝑉 𝑖𝑗

= vendor speed for each time interval i and segment j, M http://info2.scdot.org/GISMapping/Pages/GIS.aspx

𝑆𝑅

𝑖𝑗

= reference speed for each time interval i and segment j, and

T = number of all observations.

Speed data for shall have a maximum average absolute error of 5 Miles Per Hour

(MPH) in each of the following speed ranges: 0-30 MPH, >30-45 MPH, >45-60

MPH and >60 MPH.

1.2.2 Speed Error Bias (SEB) for Freeways

Speed Error Bias is defined as the average speed error (not the absolute value) in each speed range.

SEB =

𝑇

∑ ∑(𝑆𝑉

𝑖𝑗

− 𝑆𝑅

𝑖𝑗 𝑚

𝐽=1 𝑛

Speed data for Freeways shall have a maximum average error of +/- 4 MPH in each of the following speed ranges: 0-30 MPH, >30-45 MPH, >45-60 MPH and >60

MPH.

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1.2.3 Average Absolute Speed Error (AASE) for Arterials

Major Arterials (arterials with flow exceeding 20,000 AADT) shall have an AASE of 8 mph or less in the speed ranges defined as 0-15 MPH, >15- 25 MPH, >25-35

MPH and >35 MPH.

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1.2.4 Speed Error Bias for Arterials

Major Arterials shall have a maximum speed error bias of +/- 4 MPH in each of the speed ranges defined as 0-15 MPH, >15-25 MPH, >25-35 MPH and >35 MPH.

1.2.5 Accuracy requirements shall be in effect for hours when vehicle flows exceeding

500 Vehicles Per Hour (VPH) for Freeways.

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1.2.6 Accuracy requirements shall be in effect for hours when vehicle flows exceeding

500 VPH of through traffic for Arterials.

1.3 Temporal Reporting

1.3.1 Traffic data shall be provided 24 hours per day, 7 days per week. M

1.3.2 Allowance shall be made for up to 40 hours of scheduled system maintenance per year during off-peak hours.

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1.3.3 Granularity Levels

Data to be provided for the time of day and day of week in 1, 5, 15 and 60 minute time periods.

1.4 Spatial Reporting

Vendors shall/may provide travel time and speed data on:

1.4.1 Interstates M

1.4.2 Primary Routes (US and SC Routes) M

1.4.3 Interchange Ramps HD

1.4.4 Secondary Routes (≥15,000 AADT) M

1.4.5 Secondary Routes (<15,000 AADT) HD

1.4.6 Local Roads D

1.5 Spatial Referencing

1.5.1 Roadway segments are to be less than 1 mile for freeways and up to 0.3 miles for complex urban arterials. Vendor response should fully describe any higher definition segmentation, the extent to which such segmentation is open-source, uses static or dynamic referencing, and frequency of map updates.

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1.5.2 Ramps shall be reported as separate links. M

1.5.3 The Vendor shall provide traffic data for new or improved facilities within six (6) months of roadway open to traffic. Vendor shall describe process for obtaining/reporting such data as part of RFP response.

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1.5.4 The Vendor may provide link definitions which shall contain preceding and following segments.

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1.5.5 The Vendor shall not update base map more frequently than once every quarter

(three (3) months).

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1.5.6 Any Base Map update provided by the Vendor shall contain deltas from the previously supported Base Map. Segments shall be identified that have changed.

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1.5.7 The Vendor shall support a base map for at least 12 months from issuing a subsequent base map update.

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1.5.8 Segment Definitions

The Vendor shall provide segment definitions for any network segmentation supported which shall, at a minimum, contain

Beginning and ending latitude and longitude

Beginning and ending heading

Segment length

Direction of travel (unidirectional or bi-directional)

Common name

Route number

A unique identifier

1.6 Availability and Reliability

1.6.1 Note: Valid traffic data estimates occur only when sufficient base level data exists to support an estimate of the mean travel time or mean speed for a particular time period. Estimates based purely on imputation (for example, the historical average) are not considered a valid estimate in terms of the availability requirement. Periods of low flow (<500 VPH) are excluded.

The Vendor shall provide Traffic data for at least 98 percent of all covered links at all required time reporting intervals, whenever minimum flow volumes are exceeded.

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1.6.2 Availability

The Vendor shall provide Data subscription services that shall maintain at least

99.5 percent availability, determined as percent uptime of the data service excluding any scheduled system maintenance (as per 1.3.2).

1.7 Data Formatting, Packaging and Access

1.7.1 \The vendor hosted data platform should support 50-100 concurrent users for querying and downloading data

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1.7.2 Vendors shall archive data purchased by the SCDOT for a minimum of one (1) year. The archive must contain data in the same format (same fields and same temporal and spatial granularity) as it was originally accessible via an API, FTP site or equivalent interface.

1.7.3 Security M

The Vendor shall provide a password-protected web-based platform to download traffic data. The solution should have an administrative interface for managing authenticated users.

1.7.4 The vendor’s hosting solution should be a FedRAMP certified cloud-based platform.

2.0 Volume Data

The road segmentation (spatial granularity) of volume data must match that of travel time and speed data.

Respondent Comment

2.1 Base Data Elements for Historic Volume Estimates

2.1.1 Vendor shall provide historic estimated volume data reported as estimated Annual

Average Daily Traffic (AADT).

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2.1.2 Vendor shall provide historic estimated volume data reported as hourly (as opposed to daily) estimated Average Hourly Daily Traffic (AHDT) for:

day of week, month of year, season, weekday/weekend.

Example – estimated volume for Mondays from 2-3 PM is 3468 vehicles.

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2.1.2 Vendor shall provide historic estimated volume data reported as estimated Average

Daily Traffic (ADT) for:

day of week, month of year, season, weekday/weekend, a specific day of the year.

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2.1.3 Vendor shall provide historic estimated volume data reported as estimated Hourly

Volumes Flows specific:

to the day of year and to the hour of the day.

Example – estimated volume for June 5, 2019 from 2-3 PM is 3468 vehicles.

2.1.4 For any mandatory traffic volume estimates, vendor shall provide date range for HD which traffic volume estimates are available.

Example: ‘Historic AADT estimates are available for calendar year 2018 forward.’

2.1.5 Vendor may provide historic Sub-Hourly volume flows (ex: 5, 15, 30 minutes) specific:

to the day of the year and to the hour of the day.

Example – estimated volume for June 5, 2019 from 2:00-2:15 PM is 900 vehicles

2.2 Status Flag and Error Estimates

2.2.1 Status Flag

The Vendor may provide a status flag(s) per segment for each reported Traffic

Volume record to indicate whether sufficient data is available to estimate traffic volumes.

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2.2.2 Quality indicator

The Vendor may provide a numerical score that reflects the confidence or error in the estimate of the volume parameter. The intent is to provide a measure similar in concept to the standard error in the estimate of the mean. A suggested method is to use anticipated error derived from Cross-Validation techniques.

2.2.3 Vendor may provide a flag for low traffic volume situations. HD

2.3 Additional Data Feed Elements

2.3.1 The vendor may report estimated volume separately by groupings of vehicle class such as, auto, single-unit truck (FHWA vehicle class 4-7), combination-unit truck

(FHWA vehicle class 8 and above), etc.

If responding to this item, vendor shall describe how volume of different vehicle classes are obtained and/or estimated.

2.4 Volume Data Quality

2.4.1 For AADT, accuracy specifications, at a minimum, may be consistent with findings from the FHWA pooled fund project titled ‘Non-Traditional Methods to Obtain

Annual Average Daily Traffic Evaluation and Analysis Project’. These accuracy specifications reflect current fidelity of 48 hour counts relative to measured AADT.

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2.4.2 Minimum Accuracy Hourly Volume Specification: SMAPE – Minimum accuracy may be expected in the following ranges:

10-15% for High Volume roadways (Interstates and Limited access

Primary roads with higher posted speed limit)

20-25% for Mid Volume roadways (≥ 5000 AADT))

30-50% for Low Volume roadways (< 5000 AADT)

Symmetric Mean Absolute Percentage Error (SMAPE): With respect to volume estimation, the SMAPE is the average of the symmetric absolute percentage error.

The symmetric absolute percentage error is given by the absolute value of the difference between the estimated volume and the measured volume divided by the mean of the measured and estimated volume.

𝑆𝑀𝐴𝑃𝐸 =

𝑁

|𝑉𝑖 − 𝑉𝑖̂|

∗ (𝑉𝑖̂ + 𝑉𝑖)

𝑁

Where, N = sample size, 𝑉𝑖 = measured volume on segment i, and

𝑉𝑖̂ = estimated volume on segment i.

2.4.3 Minimum Accuracy Hourly Volume Specification: Coefficient of Determination

(R2) as reported against the calibration data set. Minimum R2 accuracy may be expected for the following:

90% for High Volume roadways (Interstates and Limited access Primary roads with higher posted speed limit)

80% for Mid Volume roadways ((≥ 5000 AADT)

70% for Low Volume roadways ((< 5000 AADT)

2.5 Spatial Reporting

Vendors shall/may provide volume estimates on the following facilities:

2.5.1 Interstates M

2.5.2 Primary Routes (US and SC Routes) M

2.5.3 Interchange Ramps HD

2.5.4 Secondary Routes (≥15,000 AADT) M

2.5.5 Secondary Routes (<15,000 AADT) HD

2.5.6 Local Roads D

2.5.7 Vendors shall provide a matrix of Traffic Volume Estimate type (as described in

2.1.1 to 2.1.5) indexed by road category (as described in 2.5.1 to 2.5.6). Vendors shall respond in the RFP reflective of their current ability to provide accurate traffic volume estimates.

2.6 Spatial Referencing – See Section 1.5

2.7 Data Formatting, Packaging and Access

2.7.1 The Vendor shall provide Data using prevailing industry standard formats, packaging, etc. (e.g. APIs, FTP site or similar). Vendor to provide description in response.