Junctions is a software package by Transport Research Laboratory. It incorporates the previously separate programs ARCADY, PICADY and OSCADY. The latest version, Junctions 10, was launched on 3 February 2021.

ARCADY (Assessment of Roundabout Capacity And DelaY) models traffic capacity, queues, and delays at roundabouts. The software is largely based on empirical relationships between roundabout geometry and capacity, which were established as the result of extensive research carried out on existing roundabouts on the UK road network, as well as controlled test track facilities.

The program is used by traffic engineers when assessing existing layouts or when analysing the impacts of proposed design changes. Estimates of annual accident frequencies can also be obtained. The key outputs are the Ratio of Flow to Capacity, the queue length, and delay time.

The capacity and safety relationships that ARCADY utilizes are discussed in the UK's Design Manual for Roads and Bridges.

RODEL is similar to ARCADY.

From ARCADY 7 onwards, the software has been capable of communicating with certain CAD software, aiding real-time design analysis. ARCADY 7 introduced the ability to model simple networks of linked roundabouts.

In ARCADY 8, the Highway Capacity Manual 2010 methodology for roundabout analysis was made available. ARCADY 8 also introduced a simulation technique to deal with the modelling of certain configurations, such as lane usage at roundabouts.

'ARCADY Lite' is a simplified version of ARCADY 8 that provides basic analysis of roundabouts.