missouri department of transportation speed study for gravois avenue/route 30 gravois - city of st....

8/20/2019 Missouri Department of Transportation Speed Study for Gravois Avenue/Route 30 Gravois - City of St. Louis

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The Missouri Department of Transportation (MoDOT) has performed a speed study to review the current

operating speeds on Route 30/Gravois Ave. throughout the City of St. Louis in relation to existing roadway

configurations prior to scheduled signal reconstruction and pavement overlay/striping projects.

Speed data was reviewed in eight (8) separate sections between Hampton Ave. and Tucker Blvd., each

having different configurations, land uses, and traffic volumes.

Hampton Ave. to Kingshighway Blvd.

Kingshighway Blvd. to Morgan Ford Rd.

Morgan Ford Rd. to Route 366/Chippewa St.

Route 366/Chippewa St. to Gustine Ave.

Gustine Ave. to Grand Blvd.

Grand Blvd. to Jefferson Ave.

Jefferson Ave. to Russell Blvd.

Russell Blvd. to Tucker Blvd.

Speed Study:

Route 30/Gravois Ave

St. Louis City

Revision Date: January 11, 2016


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Existing Conditions

Segment 1: Hampton Ave. to Kingshighway Blvd.

This 0.75 mile segment of Gravois has a posted speed limit of 30 MPH and carries an ADT of 17,125. The

roadway in this section consists of 4 travel lanes (2 each direction) with an on-street parking lane in each

direction. There is a bus transfer station at the northeast corner of Hampton and Gravois. Between

Hampton and Allemania, there are shopping centers with grocery stores, restaurants, a pharmacy, and a

bank. Between Allemania and Sunshine, Gravois fronts cemeteries. Between Sunshine and Quincy, the

south side of Gravois continues to front the cemetery while the north side has commercial frontage

intersected with residential cross streets. Between Quincy and Kingshighway, there is commercial

frontage along both sides of Gravois with residential streets intersecting.

The 85th

percentile speed for this segment is 44 MPH in the EB direction and 41 MPH in the WB direction.


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Segment 2: Kingshighway Blvd. to Morgan Ford Rd.

This 1.13 mile segment of Gravois has a posted speed limit of 30 MPH and carries an ADT 10,695. The

roadway in this section consists of 4 travel lanes (2 each direction) with an on-street parking lane. The

land usage in this is area is a mix of commercial and residential with Gravois primarily having commercial

frontage and the residential areas are along the cross streets immediately off of Gravois. Also,

Gardenville School is located at the northeast corner of Kingshighway and Gravois. Recently school

flashers with a school zone speed limit of 25 MPH were placed adjacent to the school along Gravois.

The 85th



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Segment 3: Morgan Ford Rd. to MO 366/Chippewa St.


roadway configuration varies significantly throughout this segment. Between Morgan Ford and Delor, a

WB left turn lane is provided to SB Morgan Ford and on-street parking does not exist in lieu of the turn

bay. Between Delor and Taft, the cross-section consists of 4 travel lanes (2 each direction) with an on-

street parking lane. Underneath the railroad viaduct between Taft and Meramec, the cross-section is only

4 travel lanes with no parking lanes. Between Meramec and Chippewa, the cross-section is a 5-lane

section with 2 lanes in each direction, a center turn lane, and on-street parking in the EB direction. The


frontage and the residential areas are along the cross streets immediately off of Gravois.

The 85th

percentile speed for this segment is 40 MPH in both directions.


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Segment 4: MO 366/Chippewa St. to Gustine Ave.

This 0.26 mile segment of Gravois has a posted speed limit of 30 MPH and carries an ADT 16,695. The

roadway in this section consists of 4 travel lanes (2 each direction) with an on-street parking lane. The

land usage in this is area is a mix of commercial and residential with Gravois having both commercial and

residential frontage along with additional residential areas along the cross streets immediately off of

Gravois.

The 85th



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Segment 5: Gustine Ave. to Grand Blvd.


roadway configuration varies throughout this segment. Between Gustine and Bamberger, the cross-

section consists of 2 travel lanes in each direction, a WB right turn lane to the shopping center opposite of

Hydraulic and to NB Gustine, and an EB on-street parking lane. Between Bamberger and Grand, the cross-

section consists of 4 travel lanes (2 each direction) with an on-street parking lane. At Grand, the roadway

widens and an EB left turn lane to NB Grand is provided. Besides the shopping center on the north side of

Gravois at Hydraulic, the land usage in this is area is a mix of commercial and residential with Gravois

having both commercial and residential frontage along with additional residential areas along the cross

streets immediately off of Gravois.

The 85th



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Segment 6: Grand Blvd. to Jefferson Ave.


roadway in this section consists of 4 travel lanes (2 each direction), a center two-way left turn lane, along

with an on-street parking lane in each direction. The land usage in this is area is a mix of commercial and

residential with Gravois having commercial frontage and the residential areas are along the cross streets

immediately off of Gravois. Also, Roosevelt High School is located at the intersection of

Gravois/Compton/Wyoming.

The 85th



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Segment 7: Jefferson Ave. to Russell Blvd.


roadway in this section consists of 6 travel lanes (3 each direction) and an on-street parking lane. The


frontage and the residential areas are along the cross streets immediately off of Gravois.

The 85th



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Segment 8: Russell Blvd. to Tucker Blvd.


roadway in this section consists of 6 travel lanes (3 each direction) and an on-street parking lane. The

outside lane in the EB direction becomes the right turn only lane to I-44 EB/I-55 NB and the outside lane

in the WB direction is an added lane from the WB I-44 exit to Gravois. The land usage in this is area is a

mix of commercial and residential with Gravois primarily having commercial frontage and the residential

areas are along the cross streets immediately off of Gravois. In addition, the intersections in this segment

serve as the gateway into the Soulard neighborhood.

The 85th


Prevailing Speed Determination

The prevailing speed is used as the primary criteria for speed limit determination in incorporated and

unincorporated areas. To determine the prevailing speed, the 85th

percentile speed was used. This is

based on the assumption that approximately 85 percent of drivers will drive at a speed that they judge to

be safe and proper. The selected speed limit is chosen in 5 mph increments such that it will not exceed

the established prevailing speed by more than 3 mph.

The selected speed limit may be less than the established prevailing speed when justified by other

criteria. This following is an overview and how it applies to Gravois.

1) Accident Rate - If the accident rate within the zone of consideration is at least 50 percent higher

than the statewide average accident rate for the same classification of highways, the prevailing speed

may be reduced by 5-10 percent. For all multi-lane roadways, the latest statewide average rate was


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521.37. The 2014 crash rate for Segment 1 was 1418.26, Segment 2 was 468.50, Segment 3 was 1180.50,

Segment 4 was 1277.96, Segment 5 was 1431.46, Segment 6 was 653.33, Segment 7 was 1184.37, and

Segment 8 was 527.91. The crash rate for Segments 1, 3, 4, 5, and 7 was high enough to warrant a 10%

reduction of the prevailing speed in those sections.

2) Access to Driveways - If a high number of driveways exist within the zone, a reduction of 5-10

percent from the prevailing speed may be justified. A Driveway Conflict Number is determined based on

the number of private or field entrances, minor commercial entrances, major commercial entrances,

industrial plant entrances, and cross streets within the zone. However, before a reduction can be made

due to driveway density it must be determined if the accident reduction is statistically significant based on

a Poisson Curve. Segments 1, 3, 4, and 5 were determined to be statistically significant; therefore the

access to driveways criteria can be used in those segments. The Driveway Conflict number was high

enough for Segments 1, 3, 4, and 5 to warrant a 10% reduction of the prevailing speed.

3) Pedestrian Traffic – Where sidewalks are not provided adjacent to the route and the total

pedestrian traffic along the route exceeds 10 per hour for 3 hours of any 8-hour period, the prevailing

speed may be reduced by 5 percent. While there are sidewalks along the majority of Gravois in the City,there are numerous signalized and unsignalized pedestrian crossings along the route. In additiion, there

have been documented crashes along with visual observations of pedestrians crossing midblock in the

absence of any traffic control. Therefore, the pedestrian traffic warrant will be applied to all segments.

4)

Parking – Where parking is permitted adjacent to the traffic lane, the prevailing speed may be

reduced by 5 percent. There is an on-street parking lane along the majority of Gravois, therefore the

parking warrant will be applied to all segments.

Recommendations

The 85

th

percentile speed, which is the base speed used for setting speed limits, for each segment alongGravois was significantly higher than the posted speed limit. However, the measured 85

th percentile

speed can be reduced, based upon the factors d iscussed above, in order to determine the prevailing

speed. The prevailing speed is the final speed used for speed limits.

Segment 1: Hampton Ave. to Kingshighway Blvd.

This segment had a measured 85th

percentile speed of 44.3 MPH in the EB direction and 41.0 MPH WB.

This segment had a crash rate almost three (3) times the statewide average, which qualifies it for a 10%

reduction of the 85th

percentile speed. The driveway density was also high enough and statistically

significant to qualify for an additional 10% reduction. In addition, the pedestrian and parking warrants

each apply a 5% reduction to the 85th

percentile speed. All of the reductions lead to a 17.7 MPH

reduction of the measured 85th

percentile speed EB and a 16.4 MPH reduction WB. Based on the higher

reductions listed, it is recommended to leave the speed in this segment at the currently posted 30 MPH.

Segment 2: Kingshighway Blvd. to Morgan Ford Rd.



The total crash rate in this segment is below the statewide average and would not qualify for reduction of

the 85th

percentile speed based on total crash history. However, the disabling crash rate was above the


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statewide average and does warrant a 10% reduction to the 85th

percentile speed. The driveway density

was not statistically significant to qualify for the driveway density reduction. However, the pedestrian and

parking warrants would each apply a 5% reduction to the 85th

percentile speed. All of the reductions lead

to an 8.5 MPH reduction of the measured 85th

percentile speed EB and a 9.1 MPH reduction WB. Based

on the higher reductions listed, it is recommended to leave the speed in this segment at the currently

posted 30 MPH.

Segment 3: Morgan Ford Rd. to MO 366/Chippewa St



This segment had a crash rate more than two (2) times the statewide average, which qualifies it for a 10%









Segment 4: MO 366/Chippewa St. to Gustine Ave.








percentile speed. All of the reductions lead to an 11.8 MPH




Segment 5: Gustine Ave. to Grand Blvd.



This segment had a crash rate almost three (3) times the statewide average, which qualifies it for a 10%







percentile speed EB and a 15.9 reduction WB. Based on the higher


Segment 6: Grand Blvd. to Jefferson Ave.

This segment had a measured 85th percentile speed of 43.1 MPH in the EB direction and 46.4 MPH WB.

The total crash rate in this segment is only 25% above the statewide average and would not qualify for


percentile speed based on total crash history. The driveway density was not

statistically significant to qualify for the driveway density reduction. However, the pedestrian and parking

warrants would each apply a 5% reduction to the 85th

percentile speed. These reductions lead to a 4.3

MPH reduction of the measured 85th

percentile speed EB and a 4.6 MPH reduction WB. Based on the


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higher reductions listed, it is recommended to leave the speed in this segment at the currently posted 35

MPH.

Segment 7: Jefferson Ave. to Russell Blvd.





percentile speed. The driveway density was not statistically significant to qualify for

the driveway density reduction. In addition, the pedestrian and parking warrants each apply a 5%

reduction to the 85th

percentile speed. All of the reductions lead to an 8.5 MPH reduction of the

measured 85th

percentile speed EB and a 9.4 MPH reduction WB. Therefore, it is recommended to leave

the speed in this segment at the currently posted 35 MPH.

Segment 8: Russell Blvd. to Tucker Blvd.



The total crash rate in this segment is just above the statewide average and would not qualify for

reduction of the 85th percentile speed based on total crash history. The driveway density was not

statistically significant to qualify for the driveway density reduction. However, the pedestrian and parking

warrants would each apply a 5% reduction to the 85th

percentile speed. These reductions lead to a 4.3

MPH reduction of the measured 85th

percentile speed EB and a 4.4 MPH reduction WB. Based on the

higher reductions listed, it is recommended to leave the speed in this segment at the currently posted 35

MPH.

Conclusion

The eight (8) segments along Gravois do not qualify for a lowered speed limit despite all of the available

reductions of the 85th

percentile speed. This is because motorists are driving these sections faster and the

reductions are not enough to bring the prevailing speed low enough for a speed limit reduction. Given

the 85th

percentile speeds and crash rates along these segments along with the pedestrian activity and on-

street parking along this corridor, it is recommended to leave all posted speed limits as is at this time.

Studies have shown simply reducing a speed limit has very little impact on the 85th

percentile speed. A

lowered speed limit with too high of an 85th

percentile speed could be more dangerous because of the

increased speed differential between the small minority of motorists that follow the speed limit no matter

what and the majority of the drivers that simply drive at the speed they feel safe. A future reduction in

the speed limit can be considered if the speeds are reduced with increased speed enforcement and/or if

the roadway reconfiguration proposed is effective at lowering the operating speeds.

missouri department of transportation speed study for gravois avenue/route 30 gravois - city of st....

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