Us Application


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Application of UK Roundabout Technology at North American sites.

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Us Application

  1. 1. Insert the title of your presentation here<br />US application/calibration of UK roundabout technology<br />Presented by Name HereJob Title - Date<br />
  2. 2. UK Roundabout Technology<br />TRL conducted extensive research in the 1950’s and 1960’s resulting in the “yield at entry” rule used to navigate and also differentiate a roundabout from other forms of intersection.<br />TRL subsequently spent 12 years researching capacity relationships at roundabouts and delivered the results to Traffic Engineers through ARCADY.<br />ARCADY has been specified as the sole software for analysis of priority roundabout design in the UK since 1981.<br />TRL is a non profit re-distributing research organisation recognised worldwide.<br />As such ARCADY is UK Roundabout Technology.<br />Copyright TRL<br />
  3. 3. Level of Service<br />Output in ARCADY 7 for each leg<br />Directly based on queuing delay<br />Data can be displayed in multiple formats<br />Copyright TRL<br />
  4. 4. Calibration<br />What is being calibrated?<br />Unusual geometry?<br />Driver behaviour?<br />Population demographics?<br />Signage / markings / clarity?<br />Prevailing weather conditions?<br />Road surface?<br />Origin / destination patterns<br />Local knowledge?<br />Local? Regional? National? Continental? Global?<br />Driver confidence of roundabout navigation<br />There has never been any attempt in the UK to derive correction factors for entire regions. ALWAYS SITE-SPECIFIC ONLY.<br />Copyright TRL<br />
  5. 5. Calibration facilities in ARCADY:1. CAPACITY SCALING <br />This scales the entire capacity (per leg)<br />Direct OR percentage<br />Example:<br />ARCADY prediction for capacity of Leg 1 = 1800 PCE/hr<br />Observed entry saturation flow for Leg 1 = 1980 PCE/hr<br />IF you believe that the difference is due to one of the reasons listed earlier and NOT due to mistakes in data entry, then:<br />Enter capacity scaling factor of 110%<br />ARCADY result will then appear as 1800 * 110% = 1980 PCE/hr and so is calibrated according to site observations<br />Copyright TRL<br />
  6. 6. Calibration facilities in ARCADY:1. CAPACITY SCALING (continued) <br />This assumption requires engineering judgement<br />Advantage is that it can be used to take into account ANY effect, no matter how complex the junction. It is applied towards the END of the modelling process, as a final adjustment<br />This is intuitively easy to understand<br />NB. It is possible to scale capacity for a roundabout network or separately for each leg which can prove more accurate in application<br />Copyright TRL<br />
  7. 7. Calibration facilities in ARCADY:1. INTERCEPT CORRECTION<br />Traditional way of adjusting ARCADY results<br />Relies on adjusting the INTERCEPT of the Qe-Qc relationship (preserving the SLOPE)<br />The INTERCEPT is the max entry flow for a GIVEN set of geometries<br />I.e., SITE-SPECIFIC<br />Correction is based on observations of the intersection<br />May be possible to derive an overall regional or national correction factor based on an average of many intersections<br />Copyright TRL<br />
  8. 8. Calibration facilities in ARCADY:1. INTERCEPT CORRECTION (continued)<br />Advantages of Intercept Correction:<br />Traditional method<br />Well established (First introduced in very early versions of ARCADY)<br />Reliable<br />Disadvantages of Intercept Correction:<br />Applied early on in the modelling process<br />Copyright TRL<br />
  9. 9. Calibration facilities in ARCADY<br />Intercept Correction<br />Copyright TRL<br />
  10. 10. Calibration facilities in ARCADY<br />What if Qe-Qc is not a linear relationship?<br />Can use Capacity Scaling but must decide whether to implement as a % scaling, or a direct scaling<br />Research continues so facilities for both options exist<br />Copyright TRL<br />
  11. 11. Copyright TRL<br />Thank You<br />North American Calibration of UK Roundabout Technology<br />Mike Hutt/ Graham Burtenshaw<br />Transportation – Traffic<br />TRL<br />United Kingdom<br /><br /><br />+44 134 477 0512<br />