What is Expansion Joint: 

       Bridge Expansion Joint can define as a joint which is designed for bridge deck to allow deck movement, deformation, expansion, or contraction due to external loads, Seismic effect, and thermal variation without disturbing the traffic.  Sealing material or filler material will retain silt, and debris and also drains the surface water to avoid any damage to the structural members under the bridge deck. 

Type Of Expansion Joints in Transverse Direction:

       Different types of expansion joints in bridges are Filler Type expansion joint, Strip seal type expansion joint, Gland slab elastomeric seal type expansion joint, Modular expansion joint, Compression seal type expansion joint, Finger type expansion joint, Sawtooth Type, etc.

Longitudinal Expansion Joints in Widen Bridges:

Traffic volume is increasing day by day. Most of the important Public Worker Depertment (PWD) roads are tacked under Ministry of Road Transeport and Highways (MoRTH) / National Highways Authority of India (NHAI). Most of the PWD roads are two lanes road. MoRTH is planning minimum four lanes road as well as six lane road as per traffic volume. 
During road widening, some good condition structures retain to reduce construction expenses. It is easy to widen a road but it is difficult to wide a bridge structure. In case of Integral abutment bridge,It was further found that the commonly observed longitudinal and diagonal cracking in the deck near the abutment on integral abutment bridges. 
In case of RCC solid slab bridge, if the bridge deck wide continuously with the help of construction joint, there is more probability to develop longitudinal cracks at construction joint.
In case of RCC deck slab (in T-beam or I-girders), cracks will be developed at deck slab in longitudinal direction due to transverse bending moment.
Longitudinal expansion joint is useful to prevent longitudinal cracks at the deck slab of widen-bridges. Now the question is what type of expansion joint shall be provided in longitudinal direction.

Image-1:  Longitudinal Expansion Joints in Widen Bridge.

 I don't have sufficient experience with longitudinal expansion joints in widened bridges. some times, I have seen filler-type extension joints in longitudinal direction in the widened bridge. But longitudinal cracks have been found on wearing coats over the longitudinal expansion joint due to unequal deflection of deck slab. Personally, I think that this is not a successful method. Filler-type expansion joints will allow water seepage through the joint. If the expansion joint is buried by bitumen surface, longitudinal crack will be developed on wearing coat over the expansion joint. 

Image-2:  Junction of Transverse and Longitudinal Expansion Joints.

Recently I have seen a widened bridge Structure where strip seal expansion joints have been provided in longitudinal direction and transverse direction. For 3 years it's working very well. It's functioning very well to date. 
I have some photographs, if you want to get the pictures please put your EMAIL ID. I will send you. I think it will be helpful to you.