"To provide responsive, innovative and effective solutions that improve quality of life."


JMD Consulting Engineers


Civil Engineering Services

JMD offers a variety of civil engineering services for transportation and land development projects. Such services cover all project development phases including planning, engineering and construction. JMD professionals develop planning level studies for civil engineering projects including master plans, concept development and feasibility studies. In addition, JMD prepares preliminary and final design for a variety of civil engineering projects including land development (e.g., site grading, drainage, etc.) and transportation facilities (e.g., highways, roadways, rail corridors, etc.). Ultimately, JMD provides construction oversight services including construction observation and inspections services of transportation and land development projects.


JMD professionals are involved on a variety of highways projects involving some of the most challenging mainline, interchange, high occupancy vehicle (HOV) and regional truckway facilities for regional transportation agencies such as Caltrans, LACMTA and Ports of Los Angeles and Long Beach. Projects include the development of studies and design including preliminary and final design.

Rail / Railroad

JMD has been involved in the development of major rail infrastructure projects designed to enhance goods movement and passenger service in the region. Major goods movement projects include the Alameda Corridor and Alameda Corridor - East grade separation program, designed to increase rail capacity and provide uninterrupted operations between existing ports and domestic destinations. Projects designed to enhance passenger service in the region include Metrolink's service expansion program.

Since its inception in 2001, JMD has become a recognized leader and expert in the design of railroad corridor crossings, grade separations and quiet zones in the region.


JMD has led the analysis and design of numerous rail/highway grade separation projects for regional agencies such as Alameda Corridor - East (ACE), LACMTA and OCTA. JMD has been involved in regional rail/highway grade separation studies such as the Orangethorpe Corridor Study for OCTA and the original Grade Separation Study for the San Gabriel Valley Council of Governments (SGVCOG) which ultimately defined the ACE Grade Separation Program which is developing 25 grade separations in the region.

JMD has served as program manager and technical advisor to ACE and OCTA on various grade separation projects and has led the design of grade separation projects, from conception to ultimate construction, including some of the most challenging grade separations, including trenches (San Gabriel Trench and Montebello Trench), underpasses (Fullerton Road), overpasses (Rosecrans Avenue) and track flyovers (Sunset Avenue/7th Avenue).


JMD professionals provide comprehensive traffic engineering services including traffic analyses and design for a variety of projects. JMD conducts traffic impact analysis, including warrant analysis, and prepares traffic impact studies for new developments as well as traffic management plans for major projects involving extensive haul and detour routes. JMD's traffic engineering group performs designs including signage, channelization, traffic signals, street and parking lot lighting.


JMD is uniquely experienced in the design of rail and bus transit facilities designed to serve passenger movement in the region. JMD has designed, following conventional design-bid-build and design-build methods, light rail facilities including guideways, stations, grade crossings, grade separations, traction power substations, utility relocation and traffic systems for nearly every light rail systems in the region including: Long Beach Blue Line, Pasadena Gold Line, Eastside Gold Line Extension, Metro Gold Line Extension (Pasadena to Azusa).

JMD has also been involved in the design of major bus rapid transit (BRT) corridors including exclusive right of way and shared lane corridors. JMD has managed the Wilshire BRT Project, Orange Line and 710 Gap BRT Corridor for LACMTA. Such projects included the design of guideways, roadways, stations, traffic signals, traffic signal priority and lighting.

Welcome to Our Website!

JMDiaz, Inc. (JMD), a California corporation, offers a full range of transportation planning and civil engineering covering highways, land development, traffic and rail projects for local agencies, railroads and private entities in California.

Originally founded by Juan M. Diaz in 2001, JMD is serving clients from its regional office in the City of Industry, California. Currently, JMD has a staff of 22 professionals and administrative staff.


Through the proven experience of its professionals and technical staff, JMD has earned a reputation of quality, commitment and responsiveness by providing innovative and timely design solutions on projects sponsored by private developers and public agencies. JMD’s reputation is complemented by its values and commitment to improve quality of life as expressed in its mission statement:


JMD is certified by local agencies as a:
Disadvantaged Business Enterprise (DBE)
Minority Business Enterprise (MBE)
Small Business Enterprise (SBE)
Community Business Enterprise (CBE)