The Division of Design (DOD) provides the procedures, policy, standards, guidance, technical assistance, and training needed to facilitate California transportation improvements and system integrity. The Design Program innovates design solutions by:
Seeking out and synthesizing information and customer feedback.
Causing the adoption of "best practices" and design information to promote safety, statewide consistency, efficiency and quality.
Assisting our customers in the application of design information and practices to facilitate the resolution of project development issues.
The diverging diamond interchange (DDI) is proving to be an efficient interchange configuration that can be used on the State highway system in addition to conventional interchange types provided in the Highway Design Manual. The DDI guidance is consistent with the Federal Highway Administration's technical publication, Diverging Diamond Interchange Informational Guide. The following is a summary of key concepts:
The primary difference between a DDI and a conventional diamond interchange is the design of ramp terminal intersections.
Directional crossover intersections on either side of the DDI divide and transpose the directions of local road traffic between the signalized crossover intersections.
DDIs remove left turning traffic between movements to and from the freeway facility at the signalized intersections.
DDIs accommodate pedestrians either along a walkway outside the traveled way or on a center walkway in the median.
DDIs accommodate bicyclists along a path that alternates between the outside and inside shoulders or along a shared use path within the center walkway.
Changes include definition updates, the use of project initiation documents and project reports, minor grammar and spelling corrections, corrections to figures, indexes and websites. Also included is revised guidance related to district delegation, superelevation, bridge barriers and railings, structure approach drainage and pavement transition details, roundabouts, ramp metering, pavement engineering and bicycle transportation design.
DIB 82-06 provides the most current understanding for accessibility in Caltrans public rights-of-way, per our agreement with the Federal Highway Administration. This guidance implements current State and Federal laws and regulations applicable to projects on the State Highway System. This DIB is primarily used as our accessibility design criteria for highways, but it is also used for scoping projects early in the project development process, as well as designing temporary pedestrian access routes during construction.
Changes include FHWA's revision from 13 to 10 controlling criteria for design as well as revised superelevation, comfort speed, and horizontal curvature guidance from the AASHTO publication, "A Policy on Geometric Design of Highways and Streets" (2011). Also included is revised guiance related to airway-highway clearances, bridge barriers and railings, roundabouts, ramp metering, and water and resource conservation. Clarifications were included related to curb ramps and necessary highway features within the clear recovery zone as well as errata that reflect current nomenclature.
Changes reflect the reorganization of river, stream, and natural channel bank protection guidance within its own Chapter 870. New Chapter 880 has been added to focus on coastal shore and inland bank protection guidance. In addition:
New discussions on geomorphology, stream processes, bio-diversity and sustainability are included in Chapter 870.
Revised rock slope protection (RSP) guidance based on FHWA Hydraulic Engineering Circular (HEC) No. 23 has been included in Chapter 870, presenting guidelines for a range of applicatins including RSP on streams and river banks, bridge piers and abutments, and bridge scour countermeasures such as guide bank and spurs.
New Chapter 880 includes a primary focus on quantifying and mitigating exposure of coastal and inland lakes to sea level rise, storm surge, and wave action.
DIB 88 provides design guidance and procedures to improve the quality and constructability of aesthetic treatments for wall structures on the State Highway System and meet the aesthetic expectations of stakeholders.