Real time parking availability estimation

Real time street parking availability estimationDr. Xu, Prof. Wolfson, Prof. Yang, Stenneth, Prof. YuUniversity of Illinois, Chicago

In one business district, vehicles searching for parking produces 730 tons of CO2, 47000 gallons on gasoline, and 38 trips around the world.

2Problemestimating street parking availability using only mobile phonesmobile phone distribution among driversGPS errors, transportation mode detection errors, Bluetooth errors, etc.

3Motivationssave time and gas to find parkingreduce congestion and pollutionmobile phone are ubiquitousaffordable - SF park 8000 parking spaces cost 23M USDexternal sensors such as cameras not utilized

4Why mobile phones ?ubiquitous with several sensors (GPS, gyro, accelerometer)several people own a mobile phoneother alternativesSensor in pavement (e.g. SF Park) $300 + $12 per month Manual reporting (e.g. Google OpenSpot) Ultrasonic sensors on taxi (e.g. ParkNet) $400 per sensor5Contributionsparking status detection (PSD)street parking estimation algorithmshistorical availability profile construction (HAP)parking availability estimation (PAE)weighted average (WA)Kalman Filter (KF)historical statistics (HS)scaled PhonePark (SPP)

6PSD, HAP, PAE

7Parking status detection (PSD)Determine when/where a driver park/deparks

Image sources: http://videos.nj.com/, http://pocketnow.com/smartphone-news/http://sf.streetsblog.org8Parking Status Detection (PSD)We proposed three schemes for PSDtransportation mode transition of driverBluetooth pairing of phone and carPay by phone piggyback

93 Schemes for PSD

Transportation mode transition (GPS/accelerometer)BluetoothPay-by-phone piggy back10HAP constructionestimates the historic mean (i.e. ) and variance (i.e. ) of parking

relevant termsprohibited period, permitted periodfalse positives, false negatives b, N

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Why is Building Profile Non-trivialLow sample rate due to low market penetration1% to 5%Errors in parking status detectionFalse negativeMissing parking activities that have occurredE.g., misclassifying parking as getting off a busFalse positive: Reporting parking activities that have not occurredE.g., misclassify getting on a bus as deparkingHistorical availability profile (HAP) AlgorithmStart with a time at which the street block is fully available, e.g., end of a prohibited time interval (start permitted period)

When a parking report is received, availability is reduced by:

Similarly when a deparking report is received

b: penetration ratio(uniform distribution)fn: false negative probabilityfp: false positive probabilityJustification:1. Each report (statistically) corresponds to 1/b actual parking2. 1/(1fn) reports should have been received if there were no false negatives3. The report is correct with 1fp probability13HAP algorithm

PP1PP2PPm

14HAP uncertainty boundingGiven an error tolerance, with what P the diff between q(t) and is less than x parking spaces.Lemma 1Lemma 2

15More specifically:

Example:If we want error < 2 with 90% confidence, standard deviation of the estimation is 10 (i.e., the average fluctuation of estimated availability at the 8:00am is 10). then we need 68 permitted periods. i.e. about two months of data.

Estimation averageEstimation varianceTrue averageNumber of samples , or permitted periodsCumulative distribution function of normal distr.16

Parking Availability Estimation (PAE)17

Parking Availability Estimation (PAE)Combining history with real timeWeighted average

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Parking Availability Estimation (PAE)combining history with real timeKalman Filter estimation (KF)

19EvaluationRT data from SFPark.org 04/10 to 08/11Polk St (12 spaces )and Chestnut St (4 spaces )

20HAP Results

Polk St. block12 spaces available

Chestnut St. block4 spaces available21PAE results

22PAE resultsBoolean availability i.e. at least one slot available b =1 %

23Related workParkNet

SFPark.org project

Googles OpenSpot

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Image sources: http://www.thesavvyboomer.com/http://pocketnow.com/smartphone-news/http://sf.streetsblog.org $300 per sensor + $12 per month service. Project cost $23 million Cumbersome$400 per system for each vehicleConclusionschemes for parking status detection (PSD)GPS, accelerometer, Bluetoothhistorical availability profile (HAP) algorithmreal time parking availability estimation algorithms (PAE)

25AcknowledgementsSF Park team (J. Primus etc.)Reviewers for fruitful commentsNSF and NURAIL26