APPENDIX B TRAFFIC IMPACT STUDY CRITERIA

APPENDIX B TRAFFIC IMPACT STUDY CRITERIA

Traffic Impact Studies Traffic impact studies (TIS) may be required by the Cunty in rder t adequately assess the impacts f a develpment prpsal n the existing and/r planned street system. A (TIS) shall be required fr prpsed develpments with peak hur trip generatin vlumes anticipated t exceed 50 vehicles during any peak hur. The primary respnsibility fr assessing the traffic impacts assciated with a prpsed develpment will rest with the applicant, with the Cunty serving in a review capacity. The fllwing shall require a written TIS: a. A rezning, inclusive f majr amendments t a planned develpment and use by special review applicatins. In the case f a rezning where the prpsed zning is anticipated t generate less traffic than the existing zning, a letter summarizing the trip generatin characteristics f the applicatin, including a cmparisn t the trip generatin characteristics f the existing zning may be submitted in lieu f a full TIS. (see Traffic Impact Study Cmpliance Letter requirements in this Appendix B) b. A preliminary plan r final plat. c. Site access is required ff a State Highway. Prir t issuing an access permit, apprval frm bth the Cunty and the Clrad Department f Transprtatin (CDOT) must be btained. d. Additinal access ff a State Highway t an existing use is being requested. e. Any change f use affecting access frm a State Highway. f. The applicant will be required t submit a new TIS if, after submitting the riginal TIS fr any f the abve submittals, the land use intensity is increased by mre than 20% r the land use is changed s that trip generatin is increased by mre than 20%. g. The applicant will be required t update an existing TIS if the existing TIS related t the develpment is mre than tw years ld, unless the Cunty determines the cnditins have nt changed significantly. Scping the TIS Transprtatin cnsultants are required t meet with and discuss prjects with Cunty staff prir t starting the TIS. At a minimum, tpics fr discussin at such meetings will include trip generatin, directinal distributin f traffic, trip assignment, definitin f the study area, intersectins requiring capacity/level f service (LOS) analysis, and methds fr prjecting build-ut vlume. Specific requirements will vary depending n the site lcatin and develpment prpsal. The scpe f the TIS shall be cmmensurate with the scale and scpe f prbable peratinal and safety impacts t the general street system. A general guideline related t determining the extent f the study area, is t carry the analysis ut at least as far as thse areas where newly generated site traffic represents 5 percent r mre f a radway s peak hur capacity. Where site generated traffic will be less than 5 percent f the radway capacity, the study area limits wuld, at minimum, include all site accesses, Duglas Cunty Radway Design and Cnstructin Standards Page B-1

adjacent radways and adjacent majr intersectins, and at maximum wuld als include all radways and cllectr/cllectr and cllectr/arterial intersectins, extending frm the prpsed develpment t and including the intersectin with the nearest state r federal highway. The study area and/r imprvement cmmitments may extend int ther jurisdictins r incrprated areas. The TIS will be the respnsibility f the applicant and must be prepared, stamped and signed by a licensed Prfessinal Engineer registered in the State f Clrad with adequate experience in Transprtatin Engineering. Upn submissin f a draft TIS, the Cunty will review the study data surces, methds, and findings. Cmments will be prvided in a written frm. The applicant and the prject engineer will then have an pprtunity t incrprate necessary revisins prir t submitting a final reprt. TIS Frmat In rder t prvide cnsistency and t facilitate staff review f a TIS, the fllwing frmat must be fllwed in the preparatin f such studies by transprtatin cnsultants. Intrductin The intrductin prtin f the TIS must cntain the fllwing: a. Develpment Site and Study Area Bundaries A brief descriptin f the size f the land parcel, existing land uses, general terrain features, and the lcatin within the jurisdictin shall be included. The exact limits f the study area shall be based n engineering judgment, and an understanding f existing traffic cnditins surrunding the site. In all instances, hwever, the applicant, engineer, and the Cunty must mutually agree upn the study area limits. These limits will usually result frm initial discussins with staff. A vicinity map that shws the site and the study area bundaries, in relatin t the surrunding transprtatin system, must be included. b. Prpsed Develpment Descriptin The specific prpsed land use types(s) and size(s) must be identified. If the develpment is t be built in a phased manner, the types and sizes f the land use in each phase, as well as the prjected cmpletin date f each phase, shall be identified. If specific land uses are nt knwn, the mst intense use (in terms f traffic generatin) allwed by current r prpsed zning must be assumed fr the TIS. c. TIS Scpe The agreed upn scpe f the TIS, in terms f the study intersectins, driveways, and radway segments, time perids and future scenaris t be analyzed, must be briefly described. Existing Cnditins The current traffic cnditins within the study area must be identified. Duglas Cunty Radway Design and Cnstructin Standards Page B-2

a. Radway Netwrk Within the study area, the applicant must describe existing radways and intersectins including radway classificatin, speed limits, gemetrics, traffic cntrl etc. A map must be prvided shwing the lcatin f such facilities as well as surrunding land use and zning. b. Traffic Vlumes The current traffic vlumes at identified intersectins (turning mvements) and radway links (24 hur vlume cunts) fr the study time perids must be measured. At a minimum mrning and evening (A.M. and P.M.) peak perid turning mvement cunts will be required. Turning mvement vlumes fr ther perids may be required. Traffic vlumes ver tw years ld will nt be accepted. A graphic shwing these vlumes shall be included. All raw traffic cunt data (including average daily traffic vlumes and peak hur turning mvements) shall be included in the appendices f the reprt. c. Levels f Service (LOS) The current traffic peratins LOS within the study area shall be described during the identified time perids. LOS shall be determined using the peratinal methdlgy as detailed in the mst recent versin f the Highway Capacity Manual (HCM). The Cunty will prvide the apprpriate existing traffic signal timing values. All calculatins must be included in the appendices f the TIS and electrnic data files must accmpany the TIS submittal. d. Traffic Safety Analysis Analysis f available entering sight distance at all prpsed site access pints (per Chapter 4 f these Standards). Traffic crash data fr radway crridrs affected by the prpsed develpment may be required fr the TIS. The safety analysis perid will nrmally be the mst recent three years. The Cunty will specify when a traffic safety analysis will be required. Site Traffic/Trip Prjectins a. Site Trip Generatin A summary table listing type, size, the Institute f Transprtatin Engineers (ITE) Trip Generatin - Land Use Cde fr each land use in the develpment, trip generatin rates used, and the resultant ttal trips fr each time perid analyzed must be prvided. Trip generatin rates frm the mst current ITE Trip Generatin manual shall be used. In the event that data fr the prpsed develpment is unavailable, trip generatin frm similar land uses, either frm ther surces, jurisdictins, r field studies, may be used with Cunty apprval. With apprval, these surces may be used t supplement ITE Trip Generatin data. Fr phased develpments, trip generatin fr each phase, as well as develpment build-ut, shall be prvided. b. Site Trip Reductins Use f the fllwing types f trip reductin factrs may be cnsidered with apprval f the Cunty. Duglas Cunty Radway Design and Cnstructin Standards Page B-3

Pass-by factrs as published in the current ITE Trip Generatin manual. Pass-by factrs are t be used t reduce the prjected additinal ttal daily traffic t street(s) serving a prpsed develpment. They are nt t be applied directly t reduce trip generatin and turning mvement vlumes at driveways serving the prpsed develpment. Internal trip assumptins with analytical supprt. Mdal split assumptins with analytical supprt. Fr example, when the prpsed develpment is lcated in a transit riented develpment r within a quarter f a mile f a majr transit crridr, a trip reductin may be applicable. c. Site Trip Distributin The estimates f percentage distributin f trips frm the prpsed develpment t destinatins in the metr regin must be clearly stated in the reprt using the nrth, suth, east, and west cmpass pints. Trip distributin shuld be based n actual traffic data. Market studies and infrmatin cncerning rigin f trip attractins t the prpsed develpment may be used t supprt these assumptins where available. A graphic shwing the percentage f site traffic n each street must be prvided as part f the TIS. d. Traffic Assignment The directin f apprach f site-generated traffic via the area s street system must be presented in this sectin. The technical analysis steps, basic methds, and assumptins used in this wrk must be clearly stated and agreed t by the Cunty. The assumed trip distributin and assignment must represent the mst lgically traveled rutes fr drivers accessing the prpsed develpment. These rutes can be determined by bservatin f travel patterns t existing land uses in the study area. A graphic shwing the site traffic assignment n the surrunding radway netwrk must be included. Backgrund Cnditins Backgrund traffic grwth fr intersectins and radways within the study area must be determined fr the pening date f the prpsed develpment (shrt-term) and in the twenty-year planning hrizn r area build-ut (lng-range) withut influence f the prpsed site, as determined by the Cunty. Fr large develpments, analysis f additinal hrizns may be required. a. Apprved Develpments Traffic frm platted but un-built develpments within the study area, r having impact n the study area, shall be added t the apprpriate planning hrizn (based n expected level f build-ut f the apprved plat(s)). Typically this will primarily affect the backgrund traffic at the time f the pening f the prpsed develpment; hwever traffic generated by sme larger apprved prjects may nt impact the area until after pening. This traffic must be added int the twenty-year planning hrizn. b. General Grwth In additin t apprved develpments, reginal traffic grwth will affect backgrund traffic vlumes at bth analysis scenaris. Future traffic grwth shall be develped thrugh means determined apprpriate by Duglas Cunty, such as the DRCOG, Duglas Cunty Transprtatin Master Plan, grwth rate methdlgy etc. The Cunty will determine whether prpsed general traffic grwth rates are acceptable. Duglas Cunty Radway Design and Cnstructin Standards Page B-4

c. Currently Planned Radway Imprvements Radway imprvements that wuld impact traffic cnditins within the study area and that are currently planned and funded may be included in the future base cnditins, as apprpriate. Include the nature f the imprvement prject, its extent, implementatin schedule, and the agency r funding surce respnsible. d. Backgrund LOS The backgrund traffic LOS within the study area, withut influence f the prpsed site, shall be described during the identified time perids. LOS shall be determined using the peratinal methdlgy as detailed in the mst recent versin f the (HCM). The extent f vehicle queuing and its ptential impact t adjacent intersectins shall be evaluated using a Pissn s distributin methdlgy (see the Queuing Analysis sectin f this Appendix B), r ther methd apprved by the Cunty. Fr unsignalized intersectins, the current HCM methdlgy fr determining LOS shall be used t identify prjected backgrund traffic cnditins. Backgrund traffic vlumes and LOS shall be shwn in graphical frmat fr each analysis scenari studied. All LOS calculatins shall be included in an appendix t the TIS and electrnic data files must accmpany the TIS submittal. Prjected Site Traffic Impacts Traffic impacts f the prpsed develpment shall be analyzed fr the anticipated pening time frame, including all prject phases, and the identified planning hrizn. Shrt-term a. Ttal Traffic Site Opening. The ttal prjected traffic vlumes at the day f develpment cmpletin shall be determined by adding the prpsed site generated traffic t the shrt-term backgrund traffic. Ttal traffic vlumes n study area radways at prpsed pening shall be shwn in graphical frmat. b. Level f Service Site Build-ut. The LOS within the study area at develpment cmpletin shall be described during the identified time perids. LOS shall be determined using the peratinal methdlgy as detailed in the mst recent versin f the (HCM). Fr signalized intersectins and/r radway segments in zning applicatins, LOS D will be the design bjective in urban areas and LOS C will be the design bjective in nnurban areas. Urban and nnurban areas shall be determined by Cunty staff based n the Duglas Cunty Cmprehensive Master Plan. Fr all ther types f develpment (nt related t zning), LOS D will be the design bjective fr verall signalized intersectin peratin at develpment pening and build-ut. Under n circumstances shall the develpment cause a drp belw an verall LOS E at signalized intersectins fr any analysis scenari. Fr analysis f unsignalized intersectins, the current HCM methdlgy fr determining LOS shall be used t identify prjected traffic cnditins. Duglas Cunty Radway Design and Cnstructin Standards Page B-5

c. Mitigatin Site Opening. At intersectins within the study area with prjected LOS E r wrse, mitigatin measures shall be identified t bring the intersectin peratin t an acceptable level. Lng-range a. Ttal Traffic Lng-range Prjectin. The ttal prjected traffic vlume at the lng-range hrizn year shall be determined by adding the prpsed site generated traffic t the lng-term backgrund traffic. Ttal traffic vlumes at the lng-range hrizn year shall be shwn in graphical frmat. b. Level f Service Lng-range Prjectin. The lng-range LOS within the study area shall be described during the identified time perids. LOS shall be determined using the peratinal methdlgy as detailed in the mst recent versin f the HCM. The design bjective fr the lng-range LOS with the prpsed develpment shuld be n wrse than the lng-range LOS prjectins (backgrund) withut the influence f the prpsed site. The extent f queuing and its ptential impact t adjacent intersectins shall be evaluated using a Pissn s distributin methdlgy (see Queuing Analysis sectin f this Appendix B), r ther methd apprved by the Cunty. The current HCM methdlgy fr determining LOS shall be used t identify prjected traffic cnditins at unsignalized intersectins. c. Mitigatin Lng-Range Prjectin. At intersectins with unacceptable prjected LOS (as defined in b., abve), mitigatin measures shall be identified t bring intersectin peratin t an acceptable level. LOS values shall be tabulated in a single table fr all study intersectins, analyzed time perids, and analysis scenaris. All LOS calculatins shall be included in the appendices and electrnic data files must accmpany the TIS submittals. Cnclusins and Recmmendatins This chapter f the TIS is a descriptin f the study findings and shall include: a. Identified Imprvements. This sectin describes the lcatin, nature, and extent f prpsed imprvements that wuld be necessary t ensure sufficient radway capacity at design bjective LOS. A graphic f each imprvement shuld be prvided shwing the length, width and ther pertinent gemetric features f the prpsed imprvements. b. Operatinal Analysis at Critical Pints. Anther iteratin f the LOS analysis must be described, which demnstrates the anticipated level f service as a result f making the prpsed imprvements. c. Traffic Vlume Prprtin. Percentages based n the traffic impact analysis may be required by the Cunty t identify the prprtin f traffic using varius public imprvements (bth existing and prpsed) frm several develpments within the study area. Duglas Cunty Radway Design and Cnstructin Standards Page B-6

Fair share percentage calculatins shall be based n the traffic grwth and nt a percentage f the ttal (grwth plus site) traffic. Ptential Mitigatin Measures Any type f ptential mitigatin measures, including new radways, additinal traffic lanes n existing radways, and changes t traffic cntrl are required t be apprved by Duglas Cunty. Rundabuts as Mitigatin Measures At intersectins f tw radways that are prjected t perate at a pr LOS r require signalizatin, Duglas Cunty will require evaluatin f a mdern rundabut as a mitigatin measure. Traffic Signals as Mitigatin Measures The need fr new traffic signals will be based n warrants cntained in the Manual n Unifrm Traffic Cntrl Devices (MUTCD) and any additinal warrants established by the Natinal Cmmittee n Unifrm Traffic Cntrl Devices. In determining the lcatin f a new signal, traffic prgressin is f paramunt imprtance. Generally, a spacing f ne-half mile fr all signalized intersectins shuld be maintained. This spacing is usually desirable t achieve gd speed, capacity, and ptimum signal prgressin. Pedestrian mvements must be cnsidered in the evaluatin and adequate pedestrian clearance prvided in the signal cycle split assumptins. T prvide flexibility and ensure ptimum tw-way signal prgressin, an apprved traffic engineering analysis must be made t prperly lcate all prpsed accesses that may require signalizatin. The sectin f radway t be analyzed fr signal prgressin will be determined by the Cunty and will include all existing and pssible future signalized intersectins. The prgressin pattern calculatins must use a cycle cnsistent with current signal timing plicies f the Cunty. A desirable bandwidth f 50% f the signal cycle shuld be used where existing cnditins allw. Where intersectins have n signals presently, but are expected t have signals, typically a 60% mainline, and 40% crss street cycle split shuld be assumed. Cycle split assumptins must relate t vlume assumptins in the capacity analysis f individual intersectins and cnsider pedestrian clearance times in the develpment f time/space diagrams. The green time allcated t the crss street will be n less than the time which is required fr a pedestrian t clear the main street using MUTCD standards. Thse intersectins that wuld reduce the ptimum bandwidth if a traffic signal were installed may be required t remain unsignalized and have turning mvements limited by access design r median islands. Refer t sectin 3 f the State Highway Access Cde fr signal spacing n State highways. Queuing Analysis A 95%-ile (using Pissn s distributin) queue length will be used as the basis f strage length design and verificatin f the adequacy f existing strage lengths. Alternative methdlgies, such as SynchrTM 95th percentile length calculatins may be used with Cunty apprval. At signalized intersectins, a backgrund cycle length f 120 secnds shall be assumed. Green times fr specific mvements shall be based n the mvement s prprtin f the critical lane vlume, subject t phase Duglas Cunty Radway Design and Cnstructin Standards Page B-7

minimums. Minimum greens shall be assumed t be 10 secnds fr thrugh mvements and 4 secnds fr left turns. Yellw change and red clearance intervals shall be assumed t be 3 secnds and 2 secnds, respectively fr left turn mvements and 4 secnds and 2 secnds, respectively fr thrugh mvements. Fr lane grups that have multiple lanes, a lane utilizatin factr, in accrdance with the HCM methdlgy, shall be applied t the calculatin f queue lengths. Electrnic data files must accmpany the TIS submittal. Revisins t Traffic Impact Study Revisins t the TIS must be prvided as required by the Cunty. The need t require revisins will be based n the cmpleteness f the TIS, the thrughness f the impact evaluatin, the adequacy f prpsed imprvements and mitigatin measures, and the cmpatibility f the TIS with the prpsed access and develpment plan. Traffic Impact Study Cmpliance Letter A standard TIS apprved fr a develpment that has been master planned may be used as reference fr the further develpment f individual lts r subareas. The required TIS fr subareas may take the frm f a TIS Cmpliance Letter. The applicant in this case may submit a Cmpliance Letter cnfirming the riginal standard TIS validity as related t the current applicatin. The Cunty may als require additinal infrmatin beynd the Cmpliance Letter. Cmpliance Letter Qualifying Cnditins A TIS Cmpliance Letter may be cnsidered if all f the fllwing cnditins are present: A standard TIS fr the area has been cmpleted, and accepted by the Cunty. Ttal prjected Trip Generatin (per the ITE Trip Generatin Manual) including the lt r subarea is less than r equal t the build-ut scenari assumptins in the standard TIS. Trip distributin is expected t be similar t thse prjected in the standard TIS. Access t the lt r subarea is unchanged frm the standard TIS. If the standard TIS is ut f date as determined by Cunty staff, additinal data cllectin and analysis may be required. Submittal f a Cmpliance Letter The applicant must prvide the fllwing infrmatin in a letter prepared, stamped, and signed by the transprtatin cnsultant engineer. The Cmpliance Letter shall include at a minimum the fllwing figures and tables: Intrductin/Prject Descriptin Figure: vicinity map Figure: prpsed develpment site plan Prpsed Cnditins Duglas Cunty Radway Design and Cnstructin Standards Page B-8

Site trip generatin Table: trip generatin summary Table: cmparisn f standard TIS trip generatin and prpsed site uses Cnclusins/Recmmendatins Cmpare/Cntrast standard TIS with prpsed develpment. Finding f n significant change t any site attributes including: Operatins Access Parcel layut Cnclusin page(s) f standard TIS Appendix Cver page f standard TIS Trip generatin page(s) f standard TIS Master site plan Duglas Cunty Radway Design and Cnstructin Standards Page B-9