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PGravel Roads PGravel Roads

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RATING RATING RATING Donald Walker TIC DirectorSusan Kummer Artifax Pavement Surface Evaluation and RatingGravel Roads PASER Evaluation3 gravel road are the road cross section drainageand ade ID: 355386

RATING RATING RATING Donald Walker T.I.C. Director Susan Kummer

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PGravel Roads RATING RATING RATING Donald Walker, T.I.C. Director,Susan Kummer, Artifax, Pavement Surface Evaluation and RatingGravel Roads PASER Evaluation3 gravel road are the road cross section, drainage,and adequacy of the gravel layer. The graveload cross section must contain adequate crownand good lateral drainage systems. The crownshould be approximately 6Ósurface water, and the culvert systems shouldbe clean and sized to prevent any seriousimpoundment of water against the roadway.heavy traffic. For most conditions, a minimumgravel thickness of 6Ó is required. Heavier layersare necessary for very poor soils and/or veryheavy traffic loads. Using geotextiles in verysignificantly improve the performance of agravel road.Surface distress, such as ruts and potholes,indicates a lack of strength. This could becaused by improper drainage, by lack of ade-quate gravel cover, or possibly both. Therefore,surface distress becomes an important indicatorof the primary concern for drainage and ade-oad provides to the driver also depends onsmooth ride and dust control. Therefore distresssuch as washboarding, loose rock, and dust areimportant in the overall service of the road.However, these conditions are secondary sinceence the primary evaluation of the roadway.It may be difficult to distinguish between apoorly maintained gravel road and anunimproved (dirt) road. The local road agencyoad with a gravel surface or as an unimprovedoad. A minimum of 1ÓÐ2Ó of gravel surfac-ing is generally necessary to be considered agravel road. More gravel is needed to provide a Gravel PASER Manualpresents a methodof existing roadways. It is based on under-gravel roads. To set a rating you assess both theextent of problems on the road and theappropriate repairs or reconstruction needed.common to gravel roads. Five road conditionscan be used to evaluate and rate gravel roads.CrownThe height and condition of crown, and an unrestricted slope of roadway from the center across the shoulders to the ditches.The ability of roadside ditches and under-road culverts to carry water away from the road.carry the traffic loads.ashboarding, potholes and ruts.Dust and loose aggregate.actual roadway usually involves looking fordifferent combinations of conditions.In reviewing different conditions and defects, it is important to consider their severity andextent. Generally problems begin slowly andprogressively become more serious. Slightdefects will grow into moderate and then severemore defects will show up on the surface.are and how extensive they are. EVALUATIONÑ GRAVEL LAYERraffic loads require an adequate layer of gravel to carry and distribute the needed will vary with the amount ofheavy traffic and the stability of thenormally required. Heavier layers, up to10Ó or more, are sometimes used forprovide long term service. The gradationand durability of the gravel (measured by hardness and soundness testing) areimportant. A proper gradation contains a mixture of larger aggregate (1Ó), sand-sized aggregate, and fines. Morefines (8%Ð15%) are recommended for surfacing gravel than are normallyused in base gravel. See Transportationfor more information. no gravellayer. layer. layer. No ruts or EVALUATIONÑSur SURFACE DEFORMATIONraffic action can dislodge aggregateand create a washboard effect on the surface. This washboarding orcorrugation develops across the road,perpendicular to the direction oftraffic. It is more prevalent underheavy traffic and under loose aggregate conditions. It may alsonear intersections, or in areas wheretraffic is accelerating or decelerating.Soft roadbeds and improper graderoperation can also cause washboards.Light washboarding can bemoved with routine grading. Wash-boarding that is moderate or severeoften requires scarification, cuttingdown 3Ó-4Ó, and regrading. If there is insufficient material, new gravel will be required. Select an aggregatewith sufficient fines to resist futurewashboarding.Since washboarding may be con-egrading is often required. Take careto blend the regraded sections intothe adjoining roadway. Since moistureis needed for compaction, correctingwashboarding after a rain is moreeffective. Maintain the crown, andsuper-elevation, and match bridgesand intersections when repairing Operating a motor patrol grader create corrugations during routineare recommended. Proper bladeangle and pitch, and proper tireinflation, are also essential. Severewashboarding traps water. Moderate washboarding in center of road. EVALUATIONÑSur raffic can create a surface depressionor rut over a portion of a gravel road.traffic causing minor surface ruts.Severe rutting (over 3Ó) may be causedby weak underlying soils. Poor crownSlight rutting can be removed byblading and restoring the crown. Severesoils will require improvements indrainage and addition of aggregate. Rut in wheel path needs regradingto eliminate ponding and prevent further road deterioration. Numerous ruts and very poordrainage create soft roadbedegrading and new aggregate. RATINGS ARE RELATED TO NEEDEDMAINTENANCE OR REPAIRNewly constructed road. Excellent crownand drainage. No maintenance required.Good crown and drainage. Routine main-Roadway shows traffic effects. Needs reconstruction. Excellent drainage.Little or no maintenance needed. 4 Moderate loose aggregate.Slight washboarding. Recently regraded. Good crown anddrainage throughout. Adequategravel for traffic. Routine gradingand dust control may be needed. 2 Little or no roadway crown (less than 3Ó). Adequate ditches on lessthan 50% of roadway. Portions of the ditches may be filled, over-grown and/or show erosion. Some areas (25%) with little or no aggre-gate. Culverts partially full of debris. Moderate to severe washboard-ing (over 3Ó deep) over 25% of area. Moderate rutting (1Ó-3Ó), over10%-25% of area. Moderate potholes (2Ó-4Ó) over 10%-25% ofarea. Severe loose aggregate (over 4Ó). Travel at slow speeds (less than or two types. may be required; completenecessary.the crown, drainage, and gravellayer. Then review the individualmaintenance or rehabilitationnecessary. The rating shouldmaintenance or repairs required.section to become more familiar Rating surface condition RATING 4may be requiredGood crown, drainage and gravel layer.Distress limited to traffic effects such asdust, loose aggregate, and slightwashboarding. Good crown, ditches,and gravel layer. Slight traffic effects,washboarding, andloose gravel. Good crown andthroughout.for traffic effects. Plenty of crownoutine grading toand loose gravel. Rating surface condition RATING 3AIRÑ Regrading and drainageimprovement, spot gravel Adequate drainage and crown on morethan 50% of roadway. Gravel layer isimprove crown and repair wash-boarding and slight ruts or potholes. crown but ditchpartially blocked. equires regrading.Ditch cleaning Fair crown andlayer. Shallowimprovement. Rating surface condition RATING 3AIRÑ Regrading and drainageimprovement, spot gravel Fair crown andgravel layer.Needs ditchingmore crown. fair crown. A fewregr Pavement Surface Evaluation and Rating (PASER) ManualsAsphalt PASER Manual, Brick and Block PASER Manual, Concrete PASER Manual, Gravel PASER Manual,Sealcoat PASER Manual,Unimproved Roads PASER ManualLocal Road Assessment and Improvement, 2000, 16 pp.FlaggerÕs Handbook ork Zone Safety, and Utility Operations,(pocket-sized guide), 2002, 58 pp.Wisconsin Transportation Bulletins#1Understanding and Using Asphalt#2How Vehicle Loads Affect Pavement Performance#3LCCÑLife Cycle Cost Analysis#4Road Drainage#5Gravel Roads#6Using Salt and Sand for Winter Road Maintenance#7Signing for Local Roads#8Using Weight Limits to Protect Local Roads#9Pavement Markings#10Seal Coating and Other Asphalt Surface Treatments#11Compaction Improves Pavement Performance#12Roadway Safety and Guardrail#13Dust Control on Unpaved Roads#14Mailbox Safety#15Culverts-Proper Use and Installation#16Geotextiles in Road Construction/Maintenance and Erosion Control#17Managing Utility Cuts#18Roadway Management and Tort Liability in Wisconsin#19The Basics of a Good Road#20Using Recovered Materials in Highway Construction#21Setting Speed Limits on Local Roads432 North Lake Streettic@epd.engr.wisc.eduhttp://tic.engr.wisc.edu TrInformation P Gravel Roads