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Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
| REPORT |
| This report is an archived publication and may contain dated technical, contact, and link information |
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| Publication Number: FHWA-HRT-14-057 Date: February 2018 |
Publication Number: FHWA-HRT-14-057 Date: February 2018 |
The result of the data collection and post processing was a total of 245 corridors representing more than 600 mi. Table 6 and table 7 present the number and mileage of corridors by area type and land use, respectively.
Table 6. Number of corridors by area type and land use.
| Scenario | Commercial | Mixed-Use | Residential | Total |
|---|---|---|---|---|
| Urban | 34 | 32 | 27 | 93 |
| Suburban | 29 | 33 | 28 | 90 |
| Urbanizing | 27 | 13 | 22 | 62 |
| Total | 90 | 78 | 77 | 245 |
Table 7. Mileage of corridors by area type and land use.
| Scenario | Commercial (mi) | Mixed-Use (mi) | Residential (mi) | Total (mi) |
|---|---|---|---|---|
| Urban | 79.1 | 92.4 | 48.7 | 220.2 |
| Suburban | 64.3 | 119.7 | 57.0 | 241.0 |
| Urbanizing | 63.8 | 31.9 | 62.4 | 158.3 |
| Total | 207.4 | 244.1 | 168.2 | 619.5 |
The crash types of interest include total, injury, turning, rear-end, and right-angle. Note that each State has specific crash codes, and therefore, the definitions vary slightly. The crash types are identified in table 8 with the associated definitions for each region.
Table 8. Crash type definitions.
| Crash Type | Definition |
|---|---|
| Total | All regions: all crashes |
| Injury | All regions: KABC on KABCO scale |
| Turning | California: any involved vehicle making a turn Minnesota: left turn or right turn North Carolina: rear-end turn, left-turn same roadway, left-turn different roadway, right-turn same roadway, right-turn different roadway |
| Rear-end | California and Minnesota: rear-end North Carolina: rear-end slow or stop and rear-end turn |
| Right-angle | California: broadside and no vehicle turning Minnesota: right-angle North Carolina: angle |
| Note: North Carolina crashes coded as rear-end turn crashes are included in both rear-end and turning crashes. Because the specific crash types cannot be summed to get total crashes, it was decided that double-counting should not pose a problem for the crash type models. The KABCO scale is used to represent injury severity in crash reporting (K is fatal injury, A is incapacitating injury, B is non-incapacitating injury, C is possible injury, and O is property damage only). |
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The following is an overview of the data collected in each of the four regions with the corresponding summary statistics for all variables.
Data were collected for 74 corridors in North Carolina, totaling nearly 150 mi. Table 9 indicates the centerline miles of corridor data included in the models for each of the nine scenarios (urban commercial, urban mixed-use, urban residential, suburban commercial, suburban mixed-use, suburban residential, urbanizing commercial, urbanizing mixed-use, and urbanizing residential).
Table 9. North Carolina mileage by area type and land use.
| Scenario | Commercial | Mixed-Use | Residential | Total |
|---|---|---|---|---|
| Urban | 23.5 | 15.3 | 23.7 | 62.5 |
| Suburban | 11.3 | 35.8 | 9.1 | 56.2 |
| Urbanizing | 11.7 | 8.3 | 9.7 | 29.7 |
| Total | 46.5 | 59.4 | 42.5 | 148.4 |
In preparation for data analysis, variables were transformed into a format appropriate for modeling, and new variable names were assigned. Table 10 presents the variable names, brief descriptions, and summary statistics, including the number of corridors and minimum, maximum, mean, and standard deviations for all independent variables. The summary statistics are computed based on corridor-level data. For some variables, the number of corridors is fewer than 74 because a variable is not relevant to all corridors. For example, if there is no median, then the number of median openings is not a relevant variable.
Table 10. Summary statistics for North Carolina independent variables.
| Variable Name | Variable Description | Corridors | Minimum | Maximum | Mean | St. Dev. |
|---|---|---|---|---|---|---|
| PROPLANE1 | Proportion of total length with two lanes | 74 | 0.00 | 1.00 | 0.11 | 0.28 |
| PROPLANE2 | Proportion of total length with three or four lanes | 74 | 0.00 | 2.03 | 0.79 | 0.38 |
| PROPLANE3 | Proportion of total length with five or more lanes | 74 | 0.00 | 1.00 | 0.10 | 0.24 |
| PROPDIV | Proportion of total length with curb or raised concrete median | 74 | 0.00 | 2.03 | 0.50 | 0.48 |
| PROPTWLTL | Proportion of total length with a TWLTL | 74 | 0.00 | 1.00 | 0.31 | 0.40 |
| PROPUNDIV | Proportion of total length with an undivided median | 74 | 0.00 | 1.00 | 0.19 | 0.35 |
| PROPNODEV | Proportion of total length with no adjacent development | 74 | 0.00 | 1.00 | 0.11 | 0.29 |
| PROPPARTDEV | Proportion of total length with partial adjacent development | 74 | 0.00 | 2.03 | 0.86 | 0.35 |
| PROPFULLDEV | Proportion of total length with full adjacent development | 74 | 0.00 | 1.00 | 0.04 | 0.17 |
| PROPLIGHT | Proportion of total length with illumination present | 74 | 0.00 | 2.03 | 0.78 | 0.44 |
| PROPPOORPVMNT | Proportion of total length with poor pavement condition | 72 | 0.00 | 1.00 | 0.06 | 0.20 |
| PROPVC | Proportion of total length with visual clutter | 74 | 0.00 | 1.00 | 0.07 | 0.23 |
| PROPLIMCONN | Proportion of total length with limited connectivity on adjacent developments | 74 | 0.00 | 2.03 | 0.28 | 0.42 |
| PROPMODCONN | Proportion of total length with moderate connectivity on adjacent developments | 74 | 0.00 | 1.00 | 0.18 | 0.29 |
| PROPSIGCONN | Proportion of total length with significant connectivity on adjacent developments | 74 | 0.00 | 1.00 | 0.54 | 0.43 |
| PROPFRONTRD | Proportion of total length with a frontage road | 74 | 0.00 | 0.42 | 0.01 | 0.06 |
| DRWYDENS | Number of driveways/mile | 74 | 0.00 | 53.55 | 13.86 | 13.34 |
| UNSIGDENS | Number of unsignalized intersections per mile | 74 | 0.00 | 12.05 | 5.48 | 2.64 |
| ACCDENS | Number of driveways plus unsignalized intersections per mile | 74 | 0.92 | 65.60 | 19.33 | 14.78 |
| SIGDENS | Number of signalized intersections per mile | 74 | 0.00 | 9.04 | 2.37 | 1.46 |
| NODRWYS | Number of driveways | 74 | 0.00 | 112.00 | 24.91 | 25.36 |
| NOCOMFULLDRWY | Number of commercial full-movement driveways | 74 | 0.00 | 78.00 | 6.47 | 13.53 |
| NORESFULLDRWY | Number of residential full-movement driveways | 74 | 0.00 | 88.00 | 9.95 | 16.76 |
| NOCOMLIMDRWY | Number of commercial limited-movement driveways | 74 | 0.00 | 39.00 | 5.50 | 7.63 |
| NORESLIMDRWY | Number of residential limited-movement driveways | 74 | 0.00 | 40.00 | 2.99 | 7.86 |
| NOUNSIG | Number of unsignalized intersections | 74 | 0.00 | 34.00 | 10.03 | 7.21 |
| NO3LEGUNSIG | Number of 3-legged unsignalized intersections | 74 | 0.00 | 39.00 | 7.82 | 6.68 |
| NO4LEGUNSIG | Number of 4-legged unsignalized intersections | 74 | 0.00 | 15.00 | 2.55 | 2.82 |
| NO3LEGFULLUNSIG | Number of 3-legged full-movement unsignalized intersections | 74 | 0.00 | 25.00 | 5.27 | 5.22 |
| NO3LEGLIMUNSIG | Number of 3-legged limited-movement unsignalized intersections | 74 | 0.00 | 13.00 | 2.35 | 2.67 |
| NO3LEGRIROUNSIG | Number of 3-legged right-in/right-out unsignalized intersections | 74 | 0.00 | 11.00 | 2.19 | 2.45 |
| NO3LEGLFMOUNSIG | Number of 3-legged unsignalized intersections with no left-turn movement from crossroad | 74 | 0.00 | 3.00 | 0.16 | 0.50 |
| NO4LEGFULLUNSIG | Number of 4-legged full-movement unsignalized intersections | 74 | 0.00 | 15.00 | 2.15 | 2.43 |
| NO4LEGLIMUNSIG | Number of 4-legged limited-movement unsignalized intersections | 74 | 0.00 | 2.00 | 0.22 | 0.53 |
| NO4LEGRIROUNSIG | Number of 4-legged right-in/right-out unsignalized intersections | 74 | 0.00 | 1.00 | 0.11 | 0.31 |
| NO4LEGLFMOUNSIG | Number of 4-legged unsignalized intersections with no left-turn movement from crossroad | 74 | 0.00 | 2.00 | 0.11 | 0.39 |
| NORTLUNSIG | Number of unsignalized intersections with a right-turn lane | 74 | 0.00 | 14.00 | 1.76 | 2.44 |
| NOLTLUNSIG | Number of unsignalized intersections with a left-turn lane | 74 | 0.00 | 31.00 | 6.53 | 7.02 |
| NOSIG | Number of signalized intersections | 74 | 0.00 | 15.00 | 4.27 | 3.07 |
| MINSPCSIG | Minimum spacing of signalized intersections (feet) | 64 | 201.00 | 12,228.00 | 1,841.00 | 1,822.00 |
| MAXSPCSIG | Maximum spacing of signalized intersections (feet) | 64 | 977.00 | 14,810.00 | 4,286.00 | 2,621.00 |
| NOFULLSIG | Number of full-movement signalized intersections | 74 | 0.00 | 12.00 | 3.82 | 2.65 |
| NOLIMSIG | Number of limited-movement signalized intersections | 74 | 0.00 | 3.00 | 0.22 | 0.56 |
| NOINTSIG | Number of interchange-related signalized intersections | 74 | 0.00 | 2.00 | 0.38 | 0.70 |
| NONRORSIG | Number of no-right-turn-on-red on mainline signalized intersections | 74 | 0.00 | 1.00 | 0.07 | 0.25 |
| NONLTSIG | Number of no-left-turn on mainline signalized intersections | 74 | 0.00 | 2.00 | 0.09 | 0.38 |
| NONUTURNSIG | Number of no-U-turn on mainline signalized intersections | 74 | 0.00 | 1.00 | 0.15 | 0.36 |
| NONRORXSIG | Number of no-right-turn-on-red on crossroad signalized intersections | 74 | 0.00 | 2.00 | 0.12 | 0.37 |
| NONLTSXIG | Number of no-left-turn on crossroad signalized intersections | 74 | 0.00 | 1.00 | 0.01 | 0.12 |
| NONUTURNXSIG | Number of no-U-turn on crossroad signalized intersections | 74 | 0.00 | 1.00 | 0.03 | 0.16 |
| NOLTPSIG | Number of signalized intersections with left-turn protection | 74 | 0.00 | 15.00 | 3.74 | 3.00 |
| NO3LEGSIG | Number of 3-legged signalized intersections | 74 | 0.00 | 4.00 | 0.80 | 0.94 |
| NO4LEGSIG | Number of 4-legged signalized intersections | 74 | 0.00 | 12.00 | 3.45 | 2.55 |
| NO5LEGSIG | Number of 5-legged signalized intersections | 74 | 0.00 | 1.00 | 0.03 | 0.16 |
| NORTLSIG | Number of signalized intersections with a right-turn lane on the mainline | 74 | 0.00 | 9.00 | 2.65 | 2.14 |
| NOLTLSIG | Number of signalized intersections with a left-turn lane on the mainline | 74 | 0.00 | 15.00 | 4.09 | 3.01 |
| NOMEDOP | Number of median openings | 57 | 0.00 | 15.00 | 2.56 | 3.39 |
| NOMEDOPLT | Number of median openings with a left-turn lane | 57 | 0.00 | 12.00 | 2.32 | 2.99 |
| NOMEDOPNOLT | Number of median openings without a left-turn lane | 57 | 0.00 | 6.00 | 0.25 | 1.06 |
| SPEED_LIMIT | Posted speed limit (miles per hour) | 74 | 35.00 | 55.00 | 45.00 | 4.53 |
| AVGPCTTRK | Average percentage trucks in traffic | 74 | 0.00 | 16.14 | 4.83 | 2.65 |
| AVGAADT | Average AADT; bidirectional traffic volume for a corridor | 74 | 50.00 | 46,087.00 | 18,887.00 | 10,347.00 |
| SPCOFFLT | Minimum spacing from off-ramp to available left turn onto mainline from same side of road (feet) | 22 | 376.00 | 1,991.00 | 774.00 | 392.00 |
| SPCOFFRT | Minimum spacing from off-ramp to available right turn onto mainline from same side of road (feet) | 22 | 281.00 | 1,991.00 | 735.00 | 417.00 |
| SPCON | Minimum spacing from on-ramp to available right turn onto mainline from same side of road (feet) | 23 | 0.00 | 2,446.00 | 864.00 | 684.00 |
| St. Dev. = standard deviation. | ||||||
Table 11 provides similar summary statistics for the dependent variables (i.e., number of crashes per mile per year by crash type). The dependent variable is presented as crash rate, which is the number of crashes divided by the segment length and by the years of crash data for a given corridor. The summary statistics for crash rate are presented based on corridor-level data. For example, the minimum total crash rate observed for a single corridor is 0.84 crash/mi/yr.
Table 11. Summary statistics for North Carolina dependent variables.
| Dependent Variable (crashes/mi/yr) | Corridors | Minimum | Maximum | Mean | St. Dev. |
|---|---|---|---|---|---|
| Total crashes | 74 | 0.84 | 195.31 | 28.57 | 25.91 |
| Injury crashes | 74 | 0.00 | 40.74 | 7.22 | 5.70 |
| Rear-end crashes | 74 | 0.00 | 69.63 | 12.91 | 11.76 |
| Right-angle crashes | 74 | 0.00 | 52.10 | 4.31 | 6.39 |
| Turning crashes | 74 | 0.00 | 24.44 | 4.94 | 4.73 |
| St. Dev. = standard deviation. | |||||
Data were collected for 61 corridors in Northern California, totaling more than 160 mi. Table 12 indicates the centerline miles of corridor data included in the models for each of the nine scenarios (urban commercial, urban mixed-use, urban residential, suburban commercial, suburban mixed-use, suburban residential, urbanizing commercial, urbanizing mixed-use, and urbanizing residential).
Table 12. Northern California mileage by area type and land use.
| Scenario | Commercial | Mixed-Use | Residential | Total |
|---|---|---|---|---|
| Urban | 24.80 | 36.39 | 12.50 | 73.69 |
| Suburban | 13.82 | 24.60 | 15.61 | 54.03 |
| Urbanizing | 9.54 | 8.55 | 18.30 | 36.39 |
| Total | 48.16 | 69.54 | 46.41 | 164.11 |
In preparation for data analysis, variables were transformed into a format appropriate for modeling, and new variable names were assigned. Table 13 presents the variable names, brief descriptions, and summary statistics, including the number of corridors and minimum, maximum, mean, and standard deviations for all independent variables. The summary statistics are computed based on corridor-level data. For some variables, the number of corridors is fewer than 61 because a variable is not relevant to all corridors. For example, if there is no median, then the number of median openings is not a relevant variable.
Table 13. Summary statistics for Northern California independent variables.
| Variable Name | Variable Description | Corridors | Minimum | Maximum | Mean | St. Dev. |
|---|---|---|---|---|---|---|
| PROPLANE1 | Proportion of total length with two lanes | 61 | 0.00 | 1.00 | 0.21 | 0.37 |
| PROPLANE2 | Proportion of total length with three or four lanes | 61 | 0.00 | 1.00 | 0.48 | 0.43 |
| PROPLANE3 | Proportion of total length with five or more lanes | 61 | 0.00 | 1.00 | 0.31 | 0.43 |
| PROPDIV | Proportion of total length with curb or raised concrete median | 61 | 0.00 | 1.00 | 0.57 | 0.45 |
| PROPTWLTL | Proportion of total length with a TWLTL | 61 | 0.00 | 1.00 | 0.15 | 0.28 |
| PROPUNDIV | Proportion of total length with an undivided median | 61 | 0.00 | 1.00 | 0.29 | 0.39 |
| PROPNODEV | Proportion of total length with no adjacent development | 61 | 0.00 | 1.00 | 0.05 | 0.16 |
| PROPPARTDEV | Proportion of total length with partial adjacent development | 61 | 0.00 | 1.00 | 0.56 | 0.45 |
| PROPFULLDEV | Proportion of total length with full adjacent development | 61 | 0.00 | 1.00 | 0.39 | 0.45 |
| PROPLIGHT | Proportion of total length with illumination present | 61 | 0.00 | 1.00 | 0.74 | 0.40 |
| PROPPOORPVMNT | Proportion of total length with poor pavement condition | 61 | 0.00 | 1.00 | 0.03 | 0.14 |
| PROPVC | Proportion of total length with visual clutter | 61 | 0.00 | 1.00 | 0.23 | 0.39 |
| PROPLIMCONN | Proportion of total length with limited connectivity on adjacent developments | 61 | 0.00 | 1.00 | 0.38 | 0.42 |
| PROPMODCONN | Proportion of total length with moderate connectivity on adjacent developments | 61 | 0.00 | 1.00 | 0.36 | 0.40 |
| PROPSIGCONN | Proportion of total length with significant connectivity on adjacent developments | 61 | 0.00 | 1.00 | 0.26 | 0.38 |
| PROPFRONTRD | Proportion of total length with a frontage road | 61 | 0.00 | 1.00 | 0.34 | 0.39 |
| DRWYDENS | Number of driveways per mile | 61 | 0.00 | 135.52 | 36.63 | 27.21 |
| UNSIGDENS | Number of unsignalized intersections per mile | 61 | 0.00 | 18.71 | 6.60 | 4.24 |
| ACCDENS | Number of driveways plus unsignalized intersections per mile | 61 | 0.00 | 144.14 | 43.24 | 29.28 |
| SIGDENS | Number of signalized intersections per mile | 61 | 0.00 | 9.09 | 3.69 | 2.06 |
| NODRWYS | Number of driveways | 61 | 0.00 | 627.00 | 102.57 | 130.63 |
| NOCOMFULLDRWY | Number of commercial full-movement driveways | 61 | 0.00 | 415.00 | 23.74 | 57.65 |
| NORESFULLDRWY | Number of residential full-movement driveways | 61 | 0.00 | 358.00 | 16.46 | 50.86 |
| NOCOMLIMDRWY | Number of commercial limited-movement driveways | 61 | 0.00 | 477.00 | 50.67 | 85.64 |
| NORESLIMDRWY | Number of residential limited-movement driveways | 61 | 0.00 | 382.00 | 11.70 | 49.88 |
| NOUNSIG | Number of unsignalized intersections | 61 | 0.00 | 137.00 | 17.43 | 22.03 |
| NO3LEGUNSIG | Number of 3-legged unsignalized intersections | 61 | 0.00 | 92.00 | 13.72 | 17.12 |
| NO4LEGUNSIG | Number of 4-legged unsignalized intersections | 61 | 0.00 | 45.00 | 3.67 | 7.20 |
| NO5LEGUNSIG | Number of 5-legged unsignalized intersections | 61 | 0.00 | 1.00 | 0.03 | 0.18 |
| NO3LEGFULLUNSIG | Number of 3-legged full-movement unsignalized intersections | 61 | 0.00 | 68.00 | 7.54 | 10.99 |
| NO3LEGLIMUNSIG | Number of 3-legged limited-movement unsignalized intersections | 61 | 0.00 | 36.00 | 6.34 | 9.24 |
| NO3LEGRIROUNSIG | Number of 3-legged right-in/right-out unsignalized intersections | 61 | 0.00 | 36.00 | 6.03 | 8.75 |
| NO3LEGLFMOUNSIG | Number of 3-legged unsignalized intersections with no left-turn movement from crossroad | 61 | 0.00 | 3.00 | 0.30 | 0.74 |
| NO4LEGFULLUNSIG | Number of 4-legged full-movement unsignalized intersections | 61 | 0.00 | 45.00 | 3.23 | 7.04 |
| NO4LEGLIMUNSIG | Number of 4-legged limited-movement unsignalized intersections | 61 | 0.00 | 12.00 | 0.44 | 2.16 |
| NO4LEGRIROUNSIG | Number of 4-legged right-in/right-out unsignalized intersections | 61 | 0.00 | 12.00 | 0.43 | 2.16 |
| NO4LEGLFMOUNSIG | Number of 4-legged unsignalized intersections with no left-turn movement from crossroad | 61 | 0.00 | 1.00 | 0.02 | 0.13 |
| NORTLUNSIG | Number of unsignalized intersections with a right-turn lane | 61 | 0.00 | 5.00 | 0.72 | 1.25 |
| NOLTLUNSIG | Number of unsignalized intersections with a left-turn lane | 61 | 0.00 | 89.00 | 7.90 | 13.13 |
| NOSIG | Number of signalized intersections | 61 | 0.00 | 54.00 | 9.57 | 10.34 |
| MINSPCSIG | Minimum spacing of signalized intersections (feet) | 54 | 109.00 | 4,471.00 | 992.00 | 1,093.00 |
| MAXSPCSIG | Maximum spacing of signalized intersections (feet) | 54 | 296.00 | 7,265.00 | 2,661 | 1,610.00 |
| NOFULLSIG | Number of full-movement signalized intersections | 61 | 0.00 | 54.00 | 9.57 | 10.34 |
| NOINTSIG | Number of interchange-related signalized intersections | 61 | 0.00 | 3.00 | 0.36 | 0.78 |
| NO3LEGSIG | Number of 3-legged signalized intersections | 61 | 0.00 | 14.00 | 2.34 | 2.94 |
| NO4LEGSIG | Number of 4-legged signalized intersections | 61 | 0.00 | 41.00 | 7.08 | 8.03 |
| NO5LEGSIG | Number of 5-legged signalized intersections | 61 | 0.00 | 5.00 | 0.20 | 0.75 |
| NORTLSIG | Number of signalized intersections with a right-turn lane on the mainline | 61 | 0.00 | 9.00 | 2.52 | 2.34 |
| NOLTLSIG | Number of signalized intersections with a left-turn lane on the mainline | 61 | 0.00 | 42.00 | 7.75 | 9.42 |
| NOMEDOP | Number of median openings | 57 | 0.00 | 42.00 | 4.61 | 7.87 |
| NOMEDOPLT | Number of median openings with a left-turn lane | 57 | 0.00 | 34.00 | 4.09 | 6.92 |
| NOMEDOPNOLT | Number of median openings without a left-turn lane | 57 | 0.00 | 8.00 | 0.54 | 1.64 |
| SPEED_LIMIT | Posted speed limit (miles per hour) | 61 | 25.00 | 55.00 | 39.10 | 7.39 |
| AVGAADT | Average AADT; bidirectional traffic volume for a corridor | 61 | 6,233.00 | 86,773.00 | 28,954.00 | 14,095.00 |
| SPCOFFLT | Minimum spacing from off-ramp to available left turn onto mainline from same side of road (feet) | 14 | 45.00 | 2,214.00 | 564.00 | 617.00 |
| SPCOFFRT | Minimum spacing from off-ramp to available right turn onto mainline from same side of road (feet) | 14 | 21.00 | 1,048.00 | 248.00 | 322.00 |
| SPCON | Minimum spacing from on-ramp to available right turn onto mainline from same side of road (feet) | 11 | 29.00 | 1,276.00 | 267.00 | 358.00 |
| St. Dev. = standard deviation. | ||||||
Table 14 provides similar summary statistics for the dependent variables (i.e., number of crashes per mile per year by crash type). The dependent variable is presented as crash rate, which is the number of crashes divided by the segment length and by the years of crash data for a given corridor. The summary statistics for crash rate are presented based on corridor-level data. For example, the minimum total crash rate observed for a single corridor is 0.18 crash/mi/yr.
Table 14. Summary statistics for Northern California dependent variables.
| Dependent Variable (crashes/mi/yr) | Corridors | Minimum | Maximum | Mean | St. Dev. |
|---|---|---|---|---|---|
| Total crashes | 61 | 0.18 | 64.52 | 20.16 | 15.27 |
| Injury crashes | 61 | 0.00 | 24.29 | 8.34 | 6.35 |
| Rear-end crashes | 61 | 0.00 | 25.57 | 8.82 | 7.07 |
| Right-angle crashes | 61 | 0.00 | 16.67 | 2.32 | 3.09 |
| Turning crashes | 61 | 0.00 | 17.18 | 5.23 | 4.23 |
| St. Dev. = standard deviation. | |||||
Data were collected for 51 corridors in Southern California, totaling nearly 150 mi. Table 15 indicates the centerline miles of corridor data included in the models for each of the nine scenarios (urban commercial, urban mixed-use, urban residential, suburban commercial, suburban mixed-use, suburban residential, urbanizing commercial, urbanizing mixed-use, and urbanizing residential).
Table 15. Southern California mileage by area type and land use.
| Scenario | Commercial | Mixed-Use | Residential | Total |
|---|---|---|---|---|
| Urban | 14.71 | 23.32 | 1.30 | 39.33 |
| Suburban | 22.18 | 40.20 | 14.41 | 76.79 |
| Urbanizing | 19.00 | 0.54 | 12.54 | 32.08 |
| Total | 55.89 | 64.06 | 28.25 | 148.20 |
In preparation for data analysis, variables were transformed into a format appropriate for modeling, and new variable names were assigned. Table 16 presents the variable names, brief descriptions, and summary statistics, including the number of corridors and minimum, maximum, mean, and standard deviations for all independent variables. The summary statistics are computed based on corridor-level data. For some variables, the number of corridors is fewer than 51 because a variable is not relevant to all corridors. For example, if there is no median, then the number of median openings is not a relevant variable.
Table 16. Summary statistics for Southern California independent variables.
| Variable Name | Variable Description | Corridors | Minimum | Maximum | Mean | St. Dev. |
|---|---|---|---|---|---|---|
| PROPLANE1 | Proportion of total length with two lanes | 51 | 0.00 | 1.00 | 0.05 | 0.21 |
| PROPLANE2 | Proportion of total length with three or four lanes | 51 | 0.00 | 1.00 | 0.58 | 0.45 |
| PROPLANE3 | Proportion of total length with five or more lanes | 51 | 0.00 | 1.00 | 0.30 | 0.41 |
| PROPDIV | Proportion of total length with curb or raised concrete median | 51 | 0.00 | 1.00 | 0.44 | 0.44 |
| PROPTWLTL | Proportion of total length with a TWLTL | 51 | 0.00 | 1.00 | 0.33 | 0.39 |
| PROPUNDIV | Proportion of total length with an undivided median | 51 | 0.00 | 1.00 | 0.23 | 0.36 |
| PROPNODEV | Proportion of total length with no adjacent development | 51 | 0.00 | 1.00 | 0.07 | 0.22 |
| PROPPARTDEV | Proportion of total length with partial adjacent development | 51 | 0.00 | 1.00 | 0.54 | 0.44 |
| PROPFULLDEV | Proportion of total length with full adjacent development | 51 | 0.00 | 1.00 | 0.38 | 0.43 |
| PROPLIGHT | Proportion of total length with illumination present | 51 | 0.00 | 1.00 | 0.80 | 0.36 |
| PROPPOORPVMNT | Proportion of total length with poor pavement condition | 51 | 0.00 | 1.00 | 0.00 | 0.00 |
| PROPVC | Proportion of total length with visual clutter | 51 | 0.00 | 1.00 | 0.41 | 0.44 |
| PROPLIMCONN | Proportion of total length with limited connectivity on adjacent developments | 51 | 0.00 | 1.00 | 0.62 | 0.39 |
| PROPMODCONN | Proportion of total length with moderate connectivity on adjacent developments | 51 | 0.00 | 1.00 | 0.33 | 0.37 |
| PROPSIGCONN | Proportion of total length with significant connectivity on adjacent developments | 51 | 0.00 | 1.00 | 0.05 | 0.16 |
| PROPFRONTRD | Proportion of total length with a frontage road | 50 | 0.00 | 1.00 | 0.40 | 0.41 |
| DRWYDENS | Number of driveways per mile | 51 | 0.00 | 85.71 | 29.19 | 21.58 |
| UNSIGDENS | Number of unsignalized intersections per mile | 51 | 0.00 | 16.07 | 6.14 | 4.04 |
| ACCDENS | Number of driveways plus unsignalized intersections per mile | 51 | 0.61 | 100.00 | 35.33 | 24.27 |
| SIGDENS | Number of signalized intersections per mile | 51 | 0.00 | 8.84 | 3.36 | 1.84 |
| NODRWYS | Number of driveways | 51 | 0.00 | 684.00 | 91.59 | 138.02 |
| NOCOMFULLDRWY | Number of commercial full-movement driveways | 51 | 0.00 | 448.00 | 41.88 | 75.50 |
| NORESFULLDRWY | Number of residential full-movement driveways | 51 | 0.00 | 128.00 | 10.90 | 23.00 |
| NOCOMLIMDRWY | Number of commercial limited-movement driveways | 51 | 0.00 | 614.00 | 34.49 | 92.38 |
| NORESLIMDRWY | Number of residential limited-movement driveways | 51 | 0.00 | 94.00 | 4.31 | 18.98 |
| NOUNSIG | Number of unsignalized intersections | 51 | 0.00 | 141.00 | 18.98 | 27.02 |
| NO3LEGUNSIG | Number of 3-legged unsignalized intersections | 51 | 0.00 | 102.00 | 13.80 | 19.63 |
| NO4LEGUNSIG | Number of 4-legged unsignalized intersections | 51 | 0.00 | 39.00 | 5.16 | 8.71 |
| NO5LEGUNSIG | Number of 5-legged unsignalized intersections | 51 | 0.00 | 1.00 | 0.02 | 0.14 |
| NO3LEGFULLUNSIG | Number of 3-legged full-movement unsignalized intersections | 51 | 0.00 | 56.00 | 8.57 | 11.84 |
| NO3LEGLIMUNSIG | Number of 3-legged limited-movement unsignalized intersections | 51 | 0.00 | 86.00 | 5.04 | 13.67 |
| NO3LEGRIROUNSIG | Number of 3-legged right-in/right-out unsignalized intersections | 51 | 1.00 | 82.00 | 4.65 | 12.74 |
| NO3LEGLFMOUNSIG | Number of 3-legged left from major only unsignalized intersections | 51 | 0.00 | 6.00 | 0.35 | 1.15 |
| NO4LEGFULLUNSIG | Number of 4-legged full-movement unsignalized intersections | 51 | 0.00 | 38.00 | 5.12 | 8.58 |
| NO4LEGLIMUNSIG | Number of 4-legged limited-movement unsignalized intersections | 51 | 0.00 | 1.00 | 0.04 | 0.20 |
| NO4LEGLFMOUNSIG | Number of 4-legged left from major only unsignalized intersections | 51 | 0.00 | 1.00 | 0.04 | 0.20 |
| NORTLUNSIG | Number of unsignalized intersections with a right-turn lane | 51 | 0.00 | 8.00 | 0.39 | 1.44 |
| NOLTLUNSIG | Number of unsignalized intersections with a left-turn lane | 51 | 0.00 | 84.00 | 11.20 | 16.20 |
| NOSIG | Number of signalized intersections | 51 | 0.00 | 66.00 | 9.94 | 13.93 |
| MINSPCSIG | Minimum spacing of signalized intersections (feet) | 48 | 139.00 | 5,541.00 | 1,135.00 | 1,027.00 |
| MAXSPCSIG | Maximum spacing of signalized intersections (feet) | 48 | 583.00 | 17,546.00 | 2,835.00 | 2,560.00 |
| NO3LEGSIG | Number of 3-legged signalized intersections | 51 | 0.00 | 11.00 | 1.35 | 2.00 |
| NO4LEGSIG | Number of 4-legged signalized intersections | 51 | 0.00 | 57.00 | 8.59 | 12.34 |
| NO5LEGSIG | Number of 5-legged signalized intersections | 51 | 0.00 | 1.00 | 0.02 | 0.14 |
| NORTLSIG | Number of signalized intersections with a right-turn lane on the mainline | 50 | 0.00 | 25.00 | 2.82 | 4.57 |
| NOLTLSIG | Number of signalized intersections with a left-turn lane on the mainline | 50 | 0.00 | 63.00 | 9.64 | 13.54 |
| NOMEDOP | Number of median openings | 32 | 0.00 | 40.00 | 6.31 | 10.01 |
| NOMEDOPLT | Number of median openings with a left-turn lane | 32 | 0.00 | 40.00 | 5.22 | 9.72 |
| NOMEDOPNOLT | Number of median openings without a left-turn lane | 32 | 0.00 | 7.00 | 1.09 | 2.12 |
| SPEED_LIMIT | Posted speed limit (miles per hour) | 51 | 25.00 | 55.00 | 41.96 | 5.75 |
| AVGAADT | Average AADT; bidirectional traffic volume for a corridor | 51 | 11,538.00 | 76,837.00 | 36,663.00 | 16,244.00 |
| SPCOFFLT | Minimum spacing from off-ramp to available left turn onto mainline from same side of road (feet) | 6 | 129.00 | 550.00 | 336.00 | 137.00 |
| SPCOFFRT | Minimum spacing from off-ramp to available right turn onto mainline from same side of road (feet) | 6 | 20.00 | 360.00 | 204.00 | 140.00 |
| SPCON | Minimum spacing from on-ramp to available right turn onto mainline from same side of road (feet) | 4 | 33.00 | 255.00 | 158.00 | 105.00 |
| St. Dev. = standard deviation. | ||||||
Table 17 provides similar summary statistics for the dependent variables (i.e., number of crashes per mile per year by crash type). The dependent variable is presented as crash rate, which is the number of crashes divided by the segment length and by the years of crash data for a given corridor. The summary statistics for crash rate are presented based on corridor-level data. For example, the minimum total crash rate observed for a single corridor is 1.14 crashes/mi/yr.
Table 17. Summary statistics for Southern California dependent variables.
| Dependent Variable (crashes/mi/yr) | Corridors | Minimum | Maximum | Mean | St. Dev. |
|---|---|---|---|---|---|
| Total crashes | 51 | 1.14 | 108.99 | 23.29 | 19.66 |
| Injury crashes | 51 | 0.33 | 33.61 | 10.34 | 6.55 |
| Rear-end crashes | 51 | 0.00 | 43.60 | 9.60 | 9.27 |
| Right-angle crashes | 51 | 0.00 | 14.99 | 2.46 | 2.77 |
| Turning crashes | 51 | 0.33 | 35.88 | 7.19 | 6.29 |
| St. Dev. = standard deviation. | |||||
Data were collected for 59 corridors in Minnesota, totaling nearly 160 mi. Table 18 indicates the centerline miles of corridor data included in the models for each of the nine scenarios (urban commercial, urban mixed-use, urban residential, suburban commercial, suburban mixed-use, suburban residential, urbanizing commercial, urbanizing mixed-use, and urbanizing residential).
Table 18. Minnesota mileage by area type and land use.
| Scenario | Commercial | Mixed‑Use | Residential | Total |
|---|---|---|---|---|
| Urban | 16.13 | 17.39 | 11.19 | 44.71 |
| Suburban | 17.03 | 19.12 | 17.88 | 54.03 |
| Urbanizing | 23.61 | 14.54 | 21.93 | 60.08 |
| Total | 56.77 | 51.05 | 51.00 | 158.82 |
In preparation for data analysis, variables were transformed into a format appropriate for modeling, and new variable names were assigned. Table 19 presents the variable names, brief descriptions, and summary statistics, including the number of corridors and minimum, maximum, mean, and standard deviations for all independent variables. The summary statistics are computed based on corridor-level data. For some variables, the number of corridors is fewer than 59 because a variable is not relevant to all corridors. For example, if there is no median, then the number of median openings is not a relevant variable.
Table 19. Summary statistics for Minnesota independent variables.
| Variable Name | Variable Description | Corridors | Minimum | Maximum | Mean | St. Dev. |
|---|---|---|---|---|---|---|
| PROPLANE1 | Proportion of total length with two lanes | 59 | 0.00 | 1.00 | 0.31 | 0.43 |
| PROPLANE2 | Proportion of total length with three or four lanes | 59 | 0.00 | 1.00 | 0.66 | 0.43 |
| PROPLANE3 | Proportion of total length with five or more lanes | 59 | 0.00 | 1.00 | 0.03 | 0.14 |
| PROPDIV | Proportion of total length with curb or raised concrete median | 59 | 0.00 | 1.00 | 0.55 | 0.45 |
| PROPTWLTL | Proportion of total length with a TWLTL | 59 | 0.00 | 1.00 | 0.07 | 0.21 |
| PROPUNDIV | Proportion of total length with an undivided median | 59 | 0.00 | 1.00 | 0.38 | 0.43 |
| PROPNODEV | Proportion of total length with no adjacent development | 59 | 0.00 | 0.40 | 0.02 | 0.08 |
| PROPPARTDEV | Proportion of total length with partial adjacent development | 59 | 0.00 | 1.00 | 0.86 | 0.27 |
| PROPFULLDEV | Proportion of total length with full adjacent development | 59 | 0.00 | 1.00 | 0.12 | 0.27 |
| PROPLIGHT | Proportion of total length with illumination present | 59 | 0.00 | 1.00 | 0.48 | 0.46 |
| PROPPOORPVMNT | Proportion of total length with poor pavement condition | 59 | 0.00 | 1.00 | 0.06 | 0.21 |
| PROPVC | Proportion of total length with visual clutter | 59 | 0.00 | 1.00 | 0.22 | 0.34 |
| PROPLIMCONN | Proportion of total length with limited connectivity on adjacent developments | 59 | 0.00 | 1.00 | 0.71 | 0.35 |
| PROPMODCONN | Proportion of total length with moderate connectivity on adjacent developments | 59 | 0.00 | 1.00 | 0.25 | 0.32 |
| PROPSIGCONN | Proportion of total length with significant connectivity on adjacent developments | 59 | 0.00 | 1.00 | 0.04 | 0.18 |
| PROPFRONTRD | Proportion of total length with a frontage road | 59 | 0.00 | 1.00 | 0.60 | 0.41 |
| DRWYDENS | Number of driveways per mile | 59 | 0.00 | 73.86 | 16.06 | 16.99 |
| UNSIGDENS | Number of unsignalized intersections per mile | 59 | 0.00 | 15.24 | 5.04 | 4.08 |
| ACCDENS | Number of driveways plus unsignalized intersections per mile | 59 | 0.00 | 79.72 | 21.10 | 20.02 |
| SIGDENS | Number of signalized intersections per mile | 59 | 0.21 | 7.21 | 2.64 | 1.63 |
| NODRWYS | Number of driveways | 59 | 0.00 | 221.00 | 38.19 | 45.99 |
| NOCOMFULLDRWY | Number of commercial full-movement driveways | 59 | 0.00 | 89.00 | 13.68 | 21.18 |
| NORESFULLDRWY | Number of residential full-movement driveways | 59 | 0.00 | 160.00 | 16.93 | 33.00 |
| NOCOMLIMDRWY | Number of commercial limited-movement driveways | 59 | 0.00 | 62.00 | 6.47 | 14.16 |
| NORESLIMDRWY | Number of residential limited-movement driveways | 59 | 0.00 | 15.00 | 1.10 | 2.75 |
| NOUNSIG | Number of unsignalized intersections | 59 | 0.00 | 51.00 | 12.59 | 12.61 |
| NO3LEGUNSIG | Number of 3-legged unsignalized intersections | 59 | 0.00 | 38.00 | 8.03 | 8.73 |
| NO4LEGUNSIG | Number of 4-legged unsignalized intersections | 59 | 0.00 | 22.00 | 4.47 | 5.65 |
| NO5LEGUNSIG | Number of 5-legged unsignalized intersections | 59 | 0.00 | 1.00 | 0.07 | 0.25 |
| NO3LEGFULLUNSIG | Number of 3-legged full-movement unsignalized intersections | 59 | 0.00 | 38.00 | 5.73 | 8.38 |
| NO3LEGLIMUNSIG | Number of 3-legged limited-movement unsignalized intersections | 59 | 0.00 | 12.00 | 2.32 | 3.31 |
| NO3LEGRIROUNSIG | Number of 3-legged right-in/right-out unsignalized intersections | 59 | 0.00 | 11.00 | 2.12 | 3.11 |
| NO3LEGLFMOUNSIG | Number of 3-legged left from major only unsignalized intersections | 59 | 0.00 | 2.00 | 0.20 | 0.48 |
| NO4LEGFULLUNSIG | Number of 4-legged full-movement unsignalized intersections | 59 | 0.00 | 22.00 | 4.47 | 5.66 |
| NO4LEGLIMUNSIG | Number of 4-legged limited movement unsignalized intersections | 59 | 0.00 | 1.00 | 0.02 | 0.13 |
| NORTLUNSIG | Number of unsignalized intersections with a right-turn lane | 59 | 0.00 | 19.00 | 3.32 | 4.24 |
| NOLTLUNSIG | Number of unsignalized intersections with a left-turn lane | 59 | 0.00 | 29.00 | 4.39 | 6.23 |
| NOSIG | Number of signalized intersections | 59 | 1.00 | 19.00 | 6.03 | 4.25 |
| MINSPCSIG | Minimum spacing of signalized intersections (feet) | 54 | 141.00 | 6,538.00 | 1,421.00 | 1,325.00 |
| MAXSPCSIG | Maximum spacing of signalized intersections (feet) | 54 | 143.00 | 27,595.00 | 4,007.00 | 3,997.00 |
| NO3LEGSIG | Number of 3-legged signalized intersections | 59 | 0.00 | 4.00 | 0.68 | 1.12 |
| NO4LEGSIG | Number of 4-legged signalized intersections | 59 | 1.00 | 17.00 | 5.32 | 3.73 |
| NO5LEGSIG | Number of 5-legged signalized intersections | 59 | 0.00 | 2.00 | 0.03 | 0.26 |
| NORTLSIG | Number of signalized intersections with major road right-turn lane | 59 | 0.00 | 11.00 | 3.76 | 2.88 |
| NOLTLSIG | Number of signalized intersections with major road left-turn lane | 59 | 0.00 | 17.00 | 5.03 | 3.66 |
| NOMEDOP | Number of median openings | 47 | 0.00 | 22.00 | 2.66 | 4.29 |
| NOMEDOPLT | Number of median openings with a left-turn lane | 47 | 0.00 | 17.00 | 2.45 | 3.96 |
| NOMEDOPNOLT | Number of median openings without a left-turn lane | 47 | 0.00 | 5.00 | 0.36 | 1.05 |
| SPEED_LIMIT | Posted speed limit (miles per hour) | 59 | 30.00 | 60.00 | 42.97 | 9.88 |
| AVGAADT | Average AADT; bidirectional traffic volume for a corridor | 59 | 5,423.00 | 70,333.00 | 24,111.00 | 13,794.00 |
| AVGCOMMAADT | Average commercial vehicle AADT | 59 | 101.00 | 4,038.00 | 894.00 | 709.00 |
| SPCOFFLT | Minimum spacing from off-ramp to available left turn onto mainline from same side of road (feet) | 25 | 142.00 | 2,640.00 | 831.00 | 601.00 |
| SPCOFFRT | Minimum spacing from off-ramp to available right turn onto mainline from same side of road (feet) | 25 | 142.00 | 2,640.00 | 802.00 | 598.00 |
| SPCON | Minimum spacing from on-ramp to available right turn onto mainline from same side of road (feet) | 26 | 70.00 | 3,500.00 | 723.00 | 727.00 |
| St. Dev. = standard deviation. | ||||||
Table 20 provides similar summary statistics for the dependent variables (i.e., number of crashes per mile per year by crash type). The dependent variable is presented as crash rate, which is the number of crashes divided by the segment length and by the years of crash data for a given corridor. The summary statistics for crash rate are presented based on corridor-level data. For example, the minimum total crash rate observed for a single corridor is 3.10 crashes/mi/yr.
Table 20. Summary statistics for Minnesota dependent variables.
| Dependent Variable (crashes/mi/yr) | Corridors | Minimum | Maximum | Mean | St. Dev. |
|---|---|---|---|---|---|
| Total crashes | 59 | 3.10 | 140.26 | 33.32 | 27.55 |
| Injury crashes | 59 | 1.19 | 52.39 | 11.07 | 10.80 |
| Rear-end crashes | 59 | 0.33 | 67.83 | 16.13 | 16.33 |
| Right-angle crashes | 59 | 0.36 | 27.64 | 5.72 | 6.10 |
| Turning crashes | 59 | 0.00 | 23.93 | 2.49 | 3.52 |
| St. Dev. = standard deviation. | |||||
