JCT provides consultancy services for Local Highway Authorities and Transport Planners across the UK (and occasionally overseas). We focus on LinSig, ARCADY and PICADY (JUNCTIONS) and TRANSYT, and use these either to report on existing performance and capacity or predict future performance for traffic schemes and development.
JCT have over 40 years experience of preparing, auditing, and checking traffic impact evaluations from local authorities and developer consultants.
As specialists in junction control, design and audit, you can at all times be confident that our team have the expertise needed to give your projects the attention they deserve. In addition, and most importantly, all team members have a wealth of on-site experience observing and measuring traffic behaviour at junctions.
Development Impact Testing
We work for many transport planners who wish to test the impact of a development on a junction or group of junctions. JCT will typically send the models, pdfs of the model input/output data and results summary tables. A Technical Note can also be produced as an optional extra, although these are not often required by Transport Planners that are inserting the modelling results and input/output data into their own TA.
| High St/Main St AM Peak | 2027 | 2027+D | 2032 | 2032+D | ||||
| DoS | MMQ (PCUs) |
DoS | MMQ (PCUs) |
DoS | MMQ (PCUs) |
DoS | MMQ (PCUs) |
|
| High St (N) | 79.3% | 7.2 | 85.9% | 7.1 | 80.0% | 7.4 | 86.7% | 7.1 |
| Main St (E) | 65.2% | 3.9 | 88.1% | 9.0 | 65.2% | 3.8 | 88.1% | 9.0 |
| High St (S) | 79.8% | 13.8 | 87.1% | 15.7 | 80.6% | 14.3 | 88.1% | 15.9 |
| Main St (W) | 80.4% | 10.1 | 88.0% | 12.1 | 81.2% | 10.2 | 88.8% | 12.2 |
| PRC | 12.0% | 2.2% | 10.9% | 1.4% | ||||
| Avg. Delay (s/PCU) | 46.2 | 56.3 | 46.8 | 57.4 | ||||
| Cycle Time | 90 | 90 | 90 | 90 | ||||
| File | High St Existing.lsg3x | |||||||
Design Option Testing / Mitigation Modelling
JCT will use modelling to show the impact of design improvements at a junction. This can be done using a drawing of the proposed scheme, and comparing the results to a model of the existing junction. However, the scheme can often be derived directly from the modelling, and once viable results are obtained, a drawing produced to reflect the model. This can often be the most efficient way to produce a feasible option.
Sometimes a junction can be improved significantly by incorporating some relatively minor changes, such as tweaks to the traffic signals or changes to lane marking. Models can be a powerful tool in demonstrating those improvements.
Model Auditing
JCT can provide a simple MOT service for LinSig models, in which we will produce an MOT check sheet that identifies major issues, or issues that may require further clarification. We can also update the model, to show the impact any suggested changes may have on the results. This can often save a lot of back and forth between modeller and reviewer, as it can show whether the original modelling conclusions are still applicable after changes, or not, at the first step of the review process.
The model MOTs are popular with Local Highway Authorities as well as Transport Planners who want reassurance that their or no major flaws in their modelling before submitting their TA.
Signal Control Roundabouts – LinSig
LinSig was specifically designed (from Version 2) to make it an excellent design tool for signal-controlled roundabouts. It is able to accurately reflect the impact of spiral marking and how traffic flows through the roundabout. It gives the engineer / modeller more control and graphical aids when deriving suitable signal timings, where the aim is to both provide sufficient capacity and progression through circulating stoplines.
JCT have modelled hundreds of signal-controlled roundabouts over the years, and have had a direct input into the design of many. On numerous occasions, all that is required is a simple change in lane marking. This can promote much better balance of flows across adjacent lanes, and significantly improving the throughput during the defined green period.
Network Modelling – LinSig
Producing network models is important where traffic signals at adjacent junctions are linked, and traffic can be co-ordinated across downstream stoplines.
Non-Signalled Roundabouts – ARCADY
It is something that is often missed, but we will always ensure we account for unequal lane usage, that can have significant impacts on capacity. There is a document within the Publications section that describes our methodology.