======= Review 1 ======= Relevance and timeliness Excellent (5) Technical content and scientific rigour Solid work of notable importance. (4) Novelty and originality Significant original work and novel results. (4) Quality of presentation Well written. (4) Submission Policy (Does the paper list the same author(s), title and abstract in its PDF file and EDAS registration?) yes Strong aspects (Comments to the author: what are the strong aspects of the paper?) Content:The paper has overall a good technical content and it's self and easily readable. The problem of MAC protocol reliability for VANET is well introduced and defined. The paper cites and discusses different MAC algorithms for VANETs. I believe that the idea of comparing two protocols using different techniques (CSMA, TDMA) is quite good. Simulation: The simulation is more credible, since the authors used a widely known simulator for VANETs (JiST/SWAN). The mobility model is well choosen too. The two metrics evaluated are relevant to the studied problem : reliability of MAC protocols in VANET network and especially for safety applications. Weak aspects (Comments to the author: what are the weak aspects of the paper?) It would interesting to compare others CSMA and TDMA algorithms together before generalizing the results to a "Comparaison of CSMA and TDMA" Simulation Setup: The simulation scenario can be more "realistic", as clamed, by using an in-city road map and consequent radio propagation models. Recommended changes (Recommended changes. Please indicate any changes that should be made to the paper if accepted.) The axis in the figures related to the second metric : "the maximum acces time" (ie : Fig 4, 5, 6 ) should be switched. (Number of nodes in the X-axis, the time in the Y-axis) The axis of the figures 4,5, and 6 should be switched to be easily readable. ======= Review 2 ======= Relevance and timeliness Good (4) Technical content and scientific rigour Valid work but limited contribution. (3) Novelty and originality Significant original work and novel results. (4) Quality of presentation Readable, but revision is needed in some parts. (3) Submission Policy (Does the paper list the same author(s), title and abstract in its PDF file and EDAS registration?) yes Strong aspects (Comments to the author: what are the strong aspects of the paper?) The paper is quite interesting when try to compare SoTDMA e 802.11p, as a MAC protocol for VANETs. Weak aspects (Comments to the author: what are the weak aspects of the paper?) Some aspects concerning the papers should be clarified and revised, as: 1) Why don't use this approach in urban area, where the SoTDMA and 802.11p performance using JIST/SWAN could be compared? 2) How to synchronize the slots in this scenario? 3) What are the consequences in this work if we change the heartbeat from 2Hz to 100 Hz, taking into accounting that the scenario is a highway and the cars tend to move fast? The interval used, 500ms it seems long in order to send beacons in the scenario proposed. 4) We can not identify in the simulation the transmission range utilized. 5) in section V. Results- ....In order to represent this probability as a function of distance, we discretize the distance with a step 20m. We cannot identify in figures 2 and 3. 6) The figure 1 should be revised? 7) The text needs to be revised, because there are many typos. Recommended changes (Recommended changes. Please indicate any changes that should be made to the paper if accepted.) Many aspects concerning this papers should be clarified and revised: 1) Why don't use this approach in urban area, where the SoTDMA and 802.11p performance using JIST/SWAN could be compared? 2) How to synchronize the slots in this scenario? 3) What are the consequences in this work if we change the heartbeat from 2Hz to 100 Hz, taking into accounting that the scenario is a highway and the cars tend to move fast? The interval used, 500ms it seems long in order to send beacons in the scenario proposed. 4) We can not identify in the simulation the transmission range utilized. 5) in section V. Results- ....In order to represent this probability as a function of distance, we discretize the distance with a step 20m. We cannot identify in figures 2 and 3. 6) The figure 1 should be revised? 7) The text needs to be revised, because there are many typos. ======= Review 3 ======= Relevance and timeliness Good (4) Technical content and scientific rigour Marginal work and simple contribution. Some flaws. (2) Novelty and originality Minor variations on a well investigated subject. (2) Quality of presentation Well written. (4) Submission Policy (Does the paper list the same author(s), title and abstract in its PDF file and EDAS registration?) yes Strong aspects (Comments to the author: what are the strong aspects of the paper?) The paper compares/evaluates two existing MAC protocols. The simulation environment is more realistic than existing comparisons (as reported by the authors) Weak aspects (Comments to the author: what are the weak aspects of the paper?) In my opinion the simulations/scenarios are simplistic. Also, it seems the authors talk about multi-hop neighbors (e.g., neighbors within 100 meters from the source and neighbors farther); however, nothing is said about forwarding messages! After comparing the two MACs I would have liked to see more analysis and/or the requirements for a MAC that is suitable for VANETS. This would have been the main contribution of the paper. Recommended changes (Recommended changes. Please indicate any changes that should be made to the paper if accepted.) The authors need to define the requirements/definition of a MAC (or variation of compared MACs) that's suitable for VANETs based on their comparison. ======= Review 4 ======= Relevance and timeliness Excellent (5) Technical content and scientific rigour Valid work but limited contribution. (3) Novelty and originality Some interesting ideas and results on a subject well investigated. (3) Quality of presentation Well written. (4) Submission Policy (Does the paper list the same author(s), title and abstract in its PDF file and EDAS registration?) yes Strong aspects (Comments to the author: what are the strong aspects of the paper?) In this paper, the CSMA and TDMA techniques are compared in a VANET environment. Some simulations are provided to evaluate performances of 802.11p and SoTDMA. Such a study has already be done. The contribution of the authors is to perform the simulation in a more realistic environnement. Weak aspects (Comments to the author: what are the weak aspects of the paper?) The paper ought to be enriched with an accurate description of 802.11p and SoTDMA and a qualitative analysis to complete quantitative analysis. Moreover, this way the paper becomes self-contained. Recommended changes (Recommended changes. Please indicate any changes that should be made to the paper if accepted.) The paper is well written. Here are some mistakes: simualtion and and precisley technlogy tecniques acces withou table, figure, section followed by a number require an uppercase (eg. Table I).